diff --git a/build-plugin.sh b/build-plugin.sh
index 13200c8..7ff10d0 100755
--- a/build-plugin.sh
+++ b/build-plugin.sh
@@ -2,7 +2,7 @@
 set -eu
 
 PLUGIN="u-navigator"
-VERSION="2026.06.23.r004"
+VERSION="2026.06.23.r005"
 PKG_DIR="packages"
 WORK_DIR=".plugin-build"
 PKG_NAME="${PLUGIN}-${VERSION}.tgz"
diff --git a/packages/u-navigator-2026.06.23.r004.tgz b/packages/u-navigator-2026.06.23.r004.tgz
deleted file mode 100644
index d729826..0000000
Binary files a/packages/u-navigator-2026.06.23.r004.tgz and /dev/null differ
diff --git a/packages/u-navigator-2026.06.23.r005.tgz b/packages/u-navigator-2026.06.23.r005.tgz
new file mode 100644
index 0000000..f44e4ab
Binary files /dev/null and b/packages/u-navigator-2026.06.23.r005.tgz differ
diff --git a/server/public/app.js b/server/public/app.js
index 6880894..451c2d5 100644
--- a/server/public/app.js
+++ b/server/public/app.js
@@ -10,6 +10,8 @@ const state = {
   draggedEntry: null,
   pointerDrag: null,
   suppressClickPath: null,
+  debug: [],
+  nextDebugId: 1,
   jobs: new Map(),
   nextWindowId: 1,
   zIndex: 20
@@ -25,6 +27,18 @@ const icons = {
 document.querySelector('#newExplorerButton').addEventListener('click', () => openExplorer());
 document.querySelector('#newPropertiesButton').addEventListener('click', () => openProperties());
 document.querySelector('#newQueueButton').addEventListener('click', () => openQueue());
+window.addEventListener('error', (event) => {
+  recordDebug('window.error', {
+    message: event.message,
+    source: event.filename,
+    line: event.lineno,
+    column: event.colno,
+    error: serializeError(event.error)
+  });
+});
+window.addEventListener('unhandledrejection', (event) => {
+  recordDebug('window.unhandledrejection', { reason: serializeError(event.reason) });
+});
 
 init();
 
@@ -300,18 +314,35 @@ function renderProperties(body) {
 
 function renderQueue(body) {
   const jobs = [...state.jobs.values()].reverse();
-  if (!jobs.length) {
-    body.innerHTML = '<p class="muted">Keine Transfers.</p>';
-    return;
-  }
-
-  body.innerHTML = `<div class="queue-list">${jobs.map((job) => `
+  const jobMarkup = jobs.length ? jobs.map((job) => `
     <article class="job">
       <strong>${escapeHtml(job.type)} #${escapeHtml(job.id)}</strong>
       <div class="muted">${escapeHtml(job.status)} · ${escapeHtml(job.message || '')}</div>
       <div class="progress"><div style="width:${Number(job.progress) || 0}%"></div></div>
     </article>
-  `).join('')}</div>`;
+  `).join('') : '<p class="muted">Keine Transfers.</p>';
+  const debugMarkup = state.debug.length ? state.debug.slice(-12).reverse().map((item) => `
+    <article class="debug-entry">
+      <strong>#${item.id} ${escapeHtml(item.label)}</strong>
+      <time>${escapeHtml(item.time)}</time>
+      <pre>${escapeHtml(JSON.stringify(item.data, null, 2))}</pre>
+    </article>
+  `).join('') : '<p class="muted">Noch keine Debug-Einträge.</p>';
+
+  body.innerHTML = `
+    <div class="queue-list">${jobMarkup}</div>
+    <section class="debug-log" aria-label="Debug-Protokoll">
+      <header>
+        <strong>Debug</strong>
+        <button type="button" data-action="clear-debug">Leeren</button>
+      </header>
+      ${debugMarkup}
+    </section>
+  `;
+  body.querySelector('[data-action="clear-debug"]')?.addEventListener('click', () => {
+    state.debug = [];
+    render();
+  });
 }
 
 async function loadExplorer(win, targetPath) {
@@ -332,8 +363,13 @@ async function loadExplorer(win, targetPath) {
 }
 
 async function handleDrop(event, win, targetPath) {
+  recordDebug('html.drop', {
+    targetPath,
+    types: dataTransferTypes(event),
+    files: getDroppedFiles(event).map((file) => ({ name: file.name, size: file.size }))
+  });
   if (state.config.readOnly) {
-    alert('Read-only mode ist aktiv.');
+    showError(new Error('Read-only mode ist aktiv.'));
     return;
   }
 
@@ -352,11 +388,13 @@ async function handleDrop(event, win, targetPath) {
 }
 
 async function createJob(type, source, destination) {
+  recordDebug('job.create.request', { type, source, destination });
   const job = await api(apiUrl(`job.php?action=${encodeURIComponent(type)}`), {
     method: 'POST',
     headers: { 'Content-Type': 'application/json' },
     body: JSON.stringify({ source, destination })
   });
+  recordDebug('job.create.response', job);
   state.jobs.set(job.id, job);
   pollJob(job.id);
   render();
@@ -369,13 +407,15 @@ async function reloadExplorerWindows(ids) {
 }
 
 function hasDropPayload(event) {
-  const types = [...(event.dataTransfer?.types || [])];
+  const types = dataTransferTypes(event);
   return types.includes('Files') || getDroppedFiles(event).length > 0;
 }
 
 function showError(error) {
+  const debug = recordDebug('error.shown', serializeError(error));
   const message = error?.message || String(error);
-  alert(message);
+  const detail = debug ? `\n\nDebug #${debug.id}: ${debug.label}` : '';
+  alert(`${message}${detail}`);
 }
 
 function getDroppedFiles(event) {
@@ -386,17 +426,28 @@ function getDroppedFiles(event) {
   }
 }
 
+function dataTransferTypes(event) {
+  try {
+    return [...(event.dataTransfer?.types || [])];
+  } catch (error) {
+    recordDebug('dataTransfer.types.error', serializeError(error));
+    return [];
+  }
+}
+
 function setEffectAllowed(event) {
   try {
     event.dataTransfer.effectAllowed = 'copyMove';
-  } catch {}
+  } catch (error) {
+    recordDebug('dataTransfer.effectAllowed.error', serializeError(error));
+  }
 }
 
 function setDropEffect(event, effect) {
   try {
     event.dataTransfer.dropEffect = effect;
   } catch {
-    // Browser rejected the requested cursor hint; the app-state drop still works.
+    recordDebug('dataTransfer.dropEffect.error', { effect });
   }
 }
 
@@ -406,7 +457,7 @@ async function renameEntry(win, entry) {
     return;
   }
   if (nextName.includes('/')) {
-    alert('Der Name darf keinen Slash enthalten.');
+    showError(new Error('Der Name darf keinen Slash enthalten.'));
     return;
   }
   await createJob('move', entry.path, `${dirname(entry.path)}/${nextName}`);
@@ -464,7 +515,7 @@ function renderContextMenu() {
       try {
         await action();
       } catch (error) {
-        alert(error.message);
+        showError(error);
       }
     });
     menu.appendChild(button);
@@ -488,11 +539,16 @@ function renderContextMenu() {
 }
 
 async function pollJob(id) {
-  const job = await api(apiUrl(`job.php?id=${encodeURIComponent(id)}`));
-  state.jobs.set(id, job);
-  render();
-  if (['queued', 'running', 'cancel_requested'].includes(job.status)) {
-    setTimeout(() => pollJob(id), 700);
+  try {
+    const job = await api(apiUrl(`job.php?id=${encodeURIComponent(id)}`));
+    state.jobs.set(id, job);
+    render();
+    if (['queued', 'running', 'cancel_requested'].includes(job.status)) {
+      setTimeout(() => pollJob(id), 700);
+    }
+  } catch (error) {
+    recordDebug('job.poll.error', { id, error: serializeError(error) });
+    showError(error);
   }
 }
 
@@ -540,6 +596,13 @@ function updatePropertiesWindows() {
 function startItemPointerDrag(event, win, entry) {
   if (event.button !== 0 || !entry) return;
 
+  recordDebug('pointer.start', {
+    windowId: win.id,
+    path: entry.path,
+    type: entry.type,
+    x: event.clientX,
+    y: event.clientY
+  });
   state.pointerDrag = {
     sourceWindowId: win.id,
     path: entry.path,
@@ -595,6 +658,13 @@ async function finishItemPointerDrag(event, move, up) {
   event.preventDefault();
   state.suppressClickPath = drag.path;
   const target = findPointerDropTarget(event);
+  recordDebug('pointer.finish', {
+    source: drag.path,
+    target: target ? { windowId: target.windowId, path: target.path, rowPath: target.row?.dataset?.path || null } : null,
+    copy: event.altKey,
+    x: event.clientX,
+    y: event.clientY
+  });
   if (!target) {
     return;
   }
@@ -635,14 +705,35 @@ function clearPointerDropTarget() {
 }
 
 function findPointerDropTarget(event) {
-  const element = document.elementFromPoint(event.clientX, event.clientY);
-  const windowEl = element?.closest?.('.window');
+  let element;
+  try {
+    element = document.elementFromPoint(event.clientX, event.clientY);
+  } catch (error) {
+    recordDebug('elementFromPoint.error', {
+      x: event.clientX,
+      y: event.clientY,
+      error: serializeError(error)
+    });
+    return null;
+  }
+  let windowEl;
+  try {
+    windowEl = element?.closest?.('.window');
+  } catch (error) {
+    recordDebug('closest.window.error', { error: serializeError(error), element: element?.tagName });
+    return null;
+  }
   if (!windowEl) return null;
 
   const win = state.windows.find((item) => item.id === windowEl.dataset.windowId);
   if (!win || win.kind !== 'explorer') return null;
 
-  const row = element.closest?.('.file-row');
+  let row;
+  try {
+    row = element.closest?.('.file-row');
+  } catch (error) {
+    recordDebug('closest.row.error', { error: serializeError(error), element: element?.tagName });
+  }
   if (row?.dataset.type === 'directory') {
     return { windowId: win.id, path: row.dataset.path, row };
   }
@@ -734,11 +825,18 @@ function startResizeWindow(event, win) {
 
 async function api(url, options) {
   const response = await fetchChecked(url, options);
-  return response.json();
+  try {
+    return await response.json();
+  } catch (error) {
+    recordDebug('api.json.error', { url, error: serializeError(error) });
+    throw error;
+  }
 }
 
 async function fetchChecked(url, options) {
+  recordDebug('fetch.request', { url, method: options?.method || 'GET' });
   const response = await fetch(url, options);
+  recordDebug('fetch.response', { url, status: response.status, ok: response.ok });
   if (!response.ok) {
     let message = `${response.status} ${response.statusText}`;
     try {
@@ -797,3 +895,39 @@ function clamp(value, min, max) {
 function apiUrl(path) {
   return `${API_BASE.replace(/\/$/, '')}/${path.replace(/^\//, '')}`;
 }
+
+function recordDebug(label, data = {}) {
+  const item = {
+    id: state.nextDebugId++,
+    time: new Date().toLocaleTimeString(),
+    label,
+    data
+  };
+  state.debug.push(item);
+  if (state.debug.length > 80) {
+    state.debug.splice(0, state.debug.length - 80);
+  }
+  updateQueueWindows();
+  return item;
+}
+
+function updateQueueWindows() {
+  for (const win of state.windows.filter((item) => item.kind === 'queue')) {
+    const body = workspace.querySelector(`.window[data-window-id="${win.id}"] .window-body`);
+    if (body) {
+      renderQueue(body);
+    }
+  }
+}
+
+function serializeError(error) {
+  if (!error) return null;
+  if (error instanceof Error || typeof error === 'object') {
+    return {
+      name: error.name,
+      message: error.message || String(error),
+      stack: error.stack
+    };
+  }
+  return { message: String(error) };
+}
diff --git a/server/public/styles.css b/server/public/styles.css
index eee438f..2dc191d 100644
--- a/server/public/styles.css
+++ b/server/public/styles.css
@@ -306,6 +306,43 @@
   gap: 10px;
 }
 
+.u-nav .debug-log {
+  border-top: 1px solid var(--line);
+  display: grid;
+  gap: 8px;
+  margin-top: 14px;
+  padding-top: 12px;
+}
+
+.u-nav .debug-log header {
+  align-items: center;
+  display: flex;
+  justify-content: space-between;
+}
+
+.u-nav .debug-entry {
+  background: var(--surface-2);
+  border: 1px solid var(--line);
+  border-radius: 6px;
+  padding: 8px;
+}
+
+.u-nav .debug-entry time {
+  color: var(--muted);
+  display: block;
+  font-size: 12px;
+}
+
+.u-nav .debug-entry pre {
+  color: var(--text);
+  font: 12px/1.35 ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
+  margin: 6px 0 0;
+  max-height: 140px;
+  overflow: auto;
+  white-space: pre-wrap;
+  word-break: break-word;
+}
+
 .u-nav .job {
   border: 1px solid var(--line);
   border-radius: 8px;
diff --git a/u-navigator.plg b/u-navigator.plg
index 0b08b0f..2bf3a14 100644
--- a/u-navigator.plg
+++ b/u-navigator.plg
@@ -1,7 +1,7 @@
 <!DOCTYPE PLUGIN [
 <!ENTITY name "u-navigator">
 <!ENTITY author "michael">
-<!ENTITY version "2026.06.23.r004">
+<!ENTITY version "2026.06.23.r005">
 <!ENTITY package "&name;-&version;.tgz">
 ]>
 <PLUGIN name="&name;" author="&author;" version="&version;" pluginURL="https://git.casaderoll.de/michael/Unraid-Navigator/raw/branch/main/u-navigator.plg">
@@ -14,7 +14,7 @@
 
 <FILE Name="/boot/config/plugins/&name;/&package;">
 <URL>https://git.casaderoll.de/michael/Unraid-Navigator/raw/branch/main/packages/&package;</URL>
-<MD5>da98c5f068d4f12dfddb0e7143a7aaa0</MD5>
+<MD5>1e5eb8df508f7a4e46a4c13336302d16</MD5>
 </FILE>
 
 <FILE Run="/bin/bash">