diff --git a/server/src/wled_controller/static/js/features/assets.ts b/server/src/wled_controller/static/js/features/assets.ts
index d7bd290..f1e3742 100644
--- a/server/src/wled_controller/static/js/features/assets.ts
+++ b/server/src/wled_controller/static/js/features/assets.ts
@@ -102,7 +102,10 @@ function initUploadDropzone(): void {
         dropzone.classList.remove('dragover');
         const files = e.dataTransfer?.files;
         if (files && files.length > 0) {
-            fileInput.files = files;
+            // Use DataTransfer to safely assign files cross-browser
+            const dt = new DataTransfer();
+            dt.items.add(files[0]);
+            fileInput.files = dt.files;
             showFile(files[0]);
         }
     });
@@ -183,9 +186,11 @@ async function _playAssetSound(assetId: string) {
         const blobUrl = URL.createObjectURL(blob);
         const audio = new Audio(blobUrl);
         audio.addEventListener('ended', () => URL.revokeObjectURL(blobUrl));
-        audio.play().catch(() => {});
+        audio.play().catch(() => showToast(t('asset.error.play_failed'), 'error'));
         _currentAudio = audio;
-    } catch { /* ignore playback errors */ }
+    } catch {
+        showToast(t('asset.error.play_failed'), 'error');
+    }
 }
 
 // ── Modal ──
@@ -281,13 +286,14 @@ export async function uploadAsset(): Promise<void> {
     if (params.toString()) url += `?${params.toString()}`;
 
     try {
+        // Use raw fetch for multipart — fetchWithAuth forces Content-Type: application/json
+        // which breaks the browser's automatic multipart boundary generation
         const headers = getHeaders();
-        delete headers['Content-Type']; // Let browser set multipart boundary
-        const res = await fetch(url, {
-            method: 'POST',
-            headers,
-            body: formData,
-        });
+        delete headers['Content-Type'];
+        const res = await fetch(url, { method: 'POST', headers, body: formData });
+        if (res.status === 401) {
+            throw new Error('Session expired');
+        }
         if (!res.ok) {
             const err = await res.json();
             throw new Error(err.detail || 'Upload failed');
@@ -365,8 +371,8 @@ export async function saveAssetMetadata(): Promise<void> {
             method: 'PUT',
             body: JSON.stringify({ name, description: description || null, tags }),
         });
-        if (!res!.ok) {
-            const err = await res!.json();
+        if (!res.ok) {
+            const err = await res.json();
             throw new Error(err.detail);
         }
 
@@ -407,11 +413,11 @@ export async function deleteAsset(assetId: string): Promise<void> {
 export async function restorePrebuiltAssets(): Promise<void> {
     try {
         const res = await fetchWithAuth('/assets/restore-prebuilt', { method: 'POST' });
-        if (!res!.ok) {
-            const err = await res!.json();
+        if (!res.ok) {
+            const err = await res.json();
             throw new Error(err.detail);
         }
-        const data = await res!.json();
+        const data = await res.json();
         if (data.restored_count > 0) {
             showToast(t('asset.prebuilt_restored').replace('{count}', String(data.restored_count)), 'success');
         } else {
@@ -439,7 +445,9 @@ async function _downloadAsset(assetId: string) {
         a.download = filename;
         a.click();
         URL.revokeObjectURL(blobUrl);
-    } catch { /* ignore */ }
+    } catch {
+        showToast(t('asset.error.download_failed'), 'error');
+    }
 }
 
 // ── Event delegation ──
diff --git a/server/src/wled_controller/static/locales/en.json b/server/src/wled_controller/static/locales/en.json
index f73bf0a..69714b4 100644
--- a/server/src/wled_controller/static/locales/en.json
+++ b/server/src/wled_controller/static/locales/en.json
@@ -434,6 +434,7 @@
     "confirm.turn_off_device": "Turn off this device?",
     "common.loading": "Loading...",
     "common.delete": "Delete",
+    "common.remove": "Remove",
     "common.edit": "Edit",
     "common.clone": "Clone",
     "common.none": "None",
@@ -1995,6 +1996,8 @@
     "asset.error.name_required": "Name is required",
     "asset.error.no_file": "Please select a file to upload",
     "asset.error.delete_failed": "Failed to delete asset",
+    "asset.error.play_failed": "Failed to play sound",
+    "asset.error.download_failed": "Failed to download asset",
     "asset.play": "Play",
     "asset.download": "Download",
     "asset.prebuilt": "Prebuilt",
diff --git a/server/src/wled_controller/static/locales/ru.json b/server/src/wled_controller/static/locales/ru.json
index 21a4d3b..52be816 100644
--- a/server/src/wled_controller/static/locales/ru.json
+++ b/server/src/wled_controller/static/locales/ru.json
@@ -434,6 +434,7 @@
     "confirm.turn_off_device": "Выключить это устройство?",
     "common.loading": "Загрузка...",
     "common.delete": "Удалить",
+    "common.remove": "Убрать",
     "common.edit": "Редактировать",
     "common.clone": "Клонировать",
     "common.none": "Нет",
@@ -1924,6 +1925,8 @@
     "asset.error.name_required": "Название обязательно",
     "asset.error.no_file": "Выберите файл для загрузки",
     "asset.error.delete_failed": "Не удалось удалить ресурс",
+    "asset.error.play_failed": "Не удалось воспроизвести звук",
+    "asset.error.download_failed": "Не удалось скачать ресурс",
     "asset.play": "Воспроизвести",
     "asset.download": "Скачать",
     "asset.prebuilt": "Встроенный",
diff --git a/server/src/wled_controller/static/locales/zh.json b/server/src/wled_controller/static/locales/zh.json
index 83f83fc..15555b7 100644
--- a/server/src/wled_controller/static/locales/zh.json
+++ b/server/src/wled_controller/static/locales/zh.json
@@ -434,6 +434,7 @@
     "confirm.turn_off_device": "关闭此设备？",
     "common.loading": "加载中...",
     "common.delete": "删除",
+    "common.remove": "移除",
     "common.edit": "编辑",
     "common.clone": "克隆",
     "common.none": "无",
@@ -1922,6 +1923,8 @@
     "asset.error.name_required": "名称为必填项",
     "asset.error.no_file": "请选择要上传的文件",
     "asset.error.delete_failed": "删除资源失败",
+    "asset.error.play_failed": "播放声音失败",
+    "asset.error.download_failed": "下载资源失败",
     "asset.play": "播放",
     "asset.download": "下载",
     "asset.prebuilt": "内置",
diff --git a/server/src/wled_controller/templates/modals/asset-editor.html b/server/src/wled_controller/templates/modals/asset-editor.html
index 8e1c135..1c9e4a9 100644
--- a/server/src/wled_controller/templates/modals/asset-editor.html
+++ b/server/src/wled_controller/templates/modals/asset-editor.html
@@ -2,7 +2,7 @@
     <div class="modal-content">
         <div class="modal-header">
             <h2 id="asset-editor-title" data-i18n="asset.edit">Edit Asset</h2>
-            <button class="modal-close-btn" onclick="closeAssetEditorModal()" data-i18n-aria-label="aria.close">&times;</button>
+            <button class="modal-close-btn" onclick="closeAssetEditorModal()" data-i18n-aria-label="aria.close">&#x2715;</button>
         </div>
         <div class="modal-body">
             <input type="hidden" id="asset-editor-id">
diff --git a/server/src/wled_controller/templates/modals/asset-upload.html b/server/src/wled_controller/templates/modals/asset-upload.html
index 3e8e486..bd5be06 100644
--- a/server/src/wled_controller/templates/modals/asset-upload.html
+++ b/server/src/wled_controller/templates/modals/asset-upload.html
@@ -2,7 +2,7 @@
     <div class="modal-content">
         <div class="modal-header">
             <h2 id="asset-upload-title" data-i18n="asset.upload">Upload Asset</h2>
-            <button class="modal-close-btn" onclick="closeAssetUploadModal()" data-i18n-aria-label="aria.close">&times;</button>
+            <button class="modal-close-btn" onclick="closeAssetUploadModal()" data-i18n-aria-label="aria.close">&#x2715;</button>
         </div>
         <div class="modal-body">
             <div id="asset-upload-error" class="modal-error" style="display:none"></div>
@@ -12,8 +12,8 @@
                     <label for="asset-upload-name" data-i18n="asset.name">Name:</label>
                     <button type="button" class="hint-toggle" onclick="toggleHint(this)" title="?">?</button>
                 </div>
-                <small class="input-hint" style="display:none" data-i18n="asset.name.hint">Optional display name. If blank, derived from filename.</small>
-                <input type="text" id="asset-upload-name" maxlength="100" placeholder="">
+                <small class="input-hint" style="display:none" data-i18n="asset.name.hint">Display name for this asset.</small>
+                <input type="text" id="asset-upload-name" maxlength="100">
                 <div id="asset-upload-tags-container"></div>
             </div>
 
@@ -34,7 +34,7 @@
                 <small class="input-hint" style="display:none" data-i18n="asset.file.hint">Select a file to upload (sound, image, video, or other).</small>
                 <input type="file" id="asset-upload-file" required hidden>
                 <div id="asset-upload-dropzone" class="file-dropzone" tabindex="0" role="button"
-                     aria-label="Choose file or drag and drop">
+                     data-i18n-aria-label="asset.drop_or_browse">
                     <div class="file-dropzone-icon">
                         <svg class="icon" viewBox="0 0 24 24" style="width:32px;height:32px">
                             <path d="M15 2H6a2 2 0 0 0-2 2v16a2 2 0 0 0 2 2h12a2 2 0 0 0 2-2V7Z"/>
@@ -49,7 +49,7 @@
                         <span id="asset-upload-file-name" class="file-dropzone-filename"></span>
                         <span id="asset-upload-file-size" class="file-dropzone-filesize"></span>
                         <button type="button" class="file-dropzone-remove" id="asset-upload-file-remove"
-                                title="Remove" data-i18n-title="common.remove">&times;</button>
+                                title="Remove" data-i18n-title="common.remove">&#x2715;</button>
                     </div>
                 </div>
             </div>