diff --git a/src/app/components/DeviceDetailOverlay.tsx b/src/app/components/DeviceDetailOverlay.tsx
index 164cf1d..eac3d25 100644
--- a/src/app/components/DeviceDetailOverlay.tsx
+++ b/src/app/components/DeviceDetailOverlay.tsx
@@ -2,7 +2,7 @@ import { useEffect, useState } from 'react';
 import { X, ChevronLeft, ChevronRight, Printer, HardDrive, Network, Box, FolderOpen, MoreVertical, Play, Pause, SkipForward, SkipBack, RotateCcw } from 'lucide-react';
 import { motion, AnimatePresence } from 'motion/react';
 import { toast } from 'sonner';
-import { getFileContents, joinPath } from '../webdav';
+import { fileExists, getFileContents, joinPath } from '../webdav';
 import MediaBrowser from './MediaBrowser';
 import MediaSet from './MediaSet';
 
@@ -122,38 +122,26 @@ export default function DeviceDetailOverlay({
     }
   };
 
-  // Detect if URL is part of a media set (e.g., disk1.d64, disk2.d64)
-  const detectMediaSet = () => {
-    if (!deviceData.url) return null;
-
-    const match = deviceData.url.match(/^(.+?)(\d+)(\.[^.]+)$/);
-    if (!match) return null;
-
-    const [, prefix, num, ext] = match;
-    const currentNum = parseInt(num);
-
-    // Generate potential media set
-    const mediaSet = [];
-    for (let i = 1; i <= 10; i++) {
-      mediaSet.push(`${prefix}${i}${ext}`);
-    }
-
-    return {
-      prefix,
-      extension: ext,
-      currentIndex: currentNum - 1,
-      files: mediaSet
-    };
-  };
-
   // Prefer an explicit .lst-derived mediaSet stored in config; fall back to pattern detection.
-  const mediaSetFiles: string[] | null = (() => {
+  const [mediaSetFiles, setMediaSetFiles] = useState<string[] | null>(null);
+
+  useEffect(() => {
     if (Array.isArray(deviceData.media_set) && deviceData.media_set.length > 0) {
-      return deviceData.media_set as string[];
+      setMediaSetFiles(deviceData.media_set as string[]);
+      return;
     }
-    const detected = detectMediaSet();
-    return detected ? detected.files : null;
-  })();
+    if (!deviceData.url) { setMediaSetFiles(null); return; }
+    const match = (deviceData.url as string).match(/^(.+?)(\d+)(\.[^.]+)$/);
+    if (!match) { setMediaSetFiles(null); return; }
+    const [, prefix, , ext] = match;
+    const candidates: string[] = [];
+    for (let i = 1; i <= 10; i++) candidates.push(`${prefix}${i}${ext}`);
+    let cancelled = false;
+    Promise.all(candidates.map(f => fileExists(f).catch(() => false))).then(flags => {
+      if (!cancelled) setMediaSetFiles(candidates.filter((_, i) => flags[i]));
+    });
+    return () => { cancelled = true; };
+  }, [deviceData.url, deviceData.media_set]);
 
   const switchMedia = (file: string) => {
     const path = getDevicePath();
@@ -166,11 +154,17 @@ export default function DeviceDetailOverlay({
       try {
         const text = await (await getFileContents(selectedPath)).text();
         const dir   = selectedPath.split('/').slice(0, -1).join('/') || '/';
-        const files = text.split('\n')
+        const candidates = text.split('\n')
           .map(l => l.trim())
           .filter(l => l.length > 0 && !l.startsWith('#'))
           .map(l => l.startsWith('/') ? l : joinPath(dir, l));
-        if (files.length === 0) { toast.error('Swap list is empty'); return; }
+        if (candidates.length === 0) { toast.error('Swap list is empty'); return; }
+        const existsArr = await Promise.all(candidates.map(f => fileExists(f).catch(() => false)));
+        const files = candidates.filter((_, i) => existsArr[i]);
+        if (files.length === 0) { toast.error('No files in swap list exist on device'); return; }
+        if (files.length < candidates.length) {
+          toast.warning(`${candidates.length - files.length} missing file(s) skipped from swap list`);
+        }
         const newConfig = JSON.parse(JSON.stringify(config));
         let dev = newConfig;
         for (const k of devicePath) dev = dev[k];
diff --git a/src/app/components/MediaManager.tsx b/src/app/components/MediaManager.tsx
index a174b52..057b4bb 100644
--- a/src/app/components/MediaManager.tsx
+++ b/src/app/components/MediaManager.tsx
@@ -760,14 +760,23 @@ export default function MediaManager({ initialPath = '/', rootPath, title, confi
       try {
         const text = await (await getFileContents(mountEntry.path)).text();
         const dir  = splitPath(mountEntry.path).parent;
-        const files = text.split('\n')
+        const candidates = text.split('\n')
           .map(l => l.trim())
           .filter(l => l.length > 0 && !l.startsWith('#'))
           .map(l => l.startsWith('/') ? l : joinPath(dir, l));
-        if (files.length === 0) {
+        if (candidates.length === 0) {
           toast.error(`${mountEntry.name}: swap list is empty`);
           return;
         }
+        const exists = await Promise.all(candidates.map(f => fileExists(f).catch(() => false)));
+        const files  = candidates.filter((_, i) => exists[i]);
+        if (files.length === 0) {
+          toast.error(`${mountEntry.name}: no files in swap list exist on device`);
+          return;
+        }
+        if (files.length < candidates.length) {
+          toast.warning(`${candidates.length - files.length} missing file(s) skipped from swap list`);
+        }
         dev.url      = files[0];
         dev.media_set = files;
       } catch (e: any) {