diff --git a/FileManager/AudibleFileStorage.cs b/FileManager/AudibleFileStorage.cs
index 3456597b..362e1371 100644
--- a/FileManager/AudibleFileStorage.cs
+++ b/FileManager/AudibleFileStorage.cs
@@ -36,6 +36,7 @@ namespace FileManager
             }
         }
 
+        private static object bookDirectoryFilesLocker { get; } = new();
         internal static BackgroundFileSystem BookDirectoryFiles { get; set; }
         #endregion
 
@@ -66,7 +67,7 @@ namespace FileManager
                 //If user changed the BooksDirectory, reinitialize.
                 if (StorageDirectory != BookDirectoryFiles.RootDirectory)
 				{
-                    lock (BookDirectoryFiles)
+                    lock (bookDirectoryFilesLocker)
                     {
                         if (StorageDirectory != BookDirectoryFiles.RootDirectory)
                         {
diff --git a/FileManager/BackgroundFileSystem.cs b/FileManager/BackgroundFileSystem.cs
index f4a84167..0546ac07 100644
--- a/FileManager/BackgroundFileSystem.cs
+++ b/FileManager/BackgroundFileSystem.cs
@@ -25,6 +25,8 @@ namespace FileManager
         private FileSystemWatcher fileSystemWatcher { get; set; }
         private BlockingCollection<FileSystemEventArgs> directoryChangesEvents { get; set; }
         private Task backgroundScanner { get; set; }
+
+        private object fsCacheLocker { get; } = new();
         private List<string> fsCache { get; } = new();
 
         public BackgroundFileSystem(string rootDirectory, string searchPattern, SearchOption searchOptions)
@@ -38,15 +40,13 @@ namespace FileManager
 
         public string FindFile(string regexPattern, RegexOptions options)
         {
-            lock (fsCache)
-            {
+            lock (fsCacheLocker)
                 return fsCache.FirstOrDefault(s => Regex.IsMatch(s, regexPattern, options));
-            }
         }
 
         public void RefreshFiles()
         {
-            lock (fsCache)
+            lock (fsCacheLocker)
             {
                 fsCache.Clear();
                 fsCache.AddRange(Directory.EnumerateFiles(RootDirectory, SearchPattern, SearchOption));
@@ -57,7 +57,7 @@ namespace FileManager
         {
             Stop();
 
-            lock (fsCache)
+            lock (fsCacheLocker)
                 fsCache.AddRange(Directory.EnumerateFiles(RootDirectory, SearchPattern, SearchOption));
 
             directoryChangesEvents = new BlockingCollection<FileSystemEventArgs>();
@@ -86,7 +86,7 @@ namespace FileManager
             //Dispose of directoryChangesEvents after backgroundScanner exists.
             directoryChangesEvents?.Dispose();
 
-            lock (fsCache)
+            lock (fsCacheLocker)
                 fsCache.Clear();
         }
 
@@ -106,7 +106,7 @@ namespace FileManager
         {
             while (directoryChangesEvents.TryTake(out FileSystemEventArgs change, -1))
             {
-                lock (fsCache)
+                lock (fsCacheLocker)
                     UpdateLocalCache(change);
             }
         }
@@ -146,9 +146,7 @@ namespace FileManager
         private void AddUniqueFiles(IEnumerable<string> newFiles)
         {
             foreach (var file in newFiles)
-            {
                 AddUniqueFile(file);
-            }
         }
         private void AddUniqueFile(string newFile)
         {
diff --git a/FileManager/PictureStorage.cs b/FileManager/PictureStorage.cs
index 8c143dcf..2e75f7db 100644
--- a/FileManager/PictureStorage.cs
+++ b/FileManager/PictureStorage.cs
@@ -43,11 +43,12 @@ namespace FileManager
 		public static event EventHandler<PictureCachedEventArgs> PictureCached;
 
 		private static BlockingCollection<PictureDefinition> DownloadQueue { get; } = new BlockingCollection<PictureDefinition>();
+		private static object cacheLocker { get; } = new object();
 		private static Dictionary<PictureDefinition, byte[]> cache { get; } = new Dictionary<PictureDefinition, byte[]>();
 		private static Dictionary<PictureSize, byte[]> defaultImages { get; } = new Dictionary<PictureSize, byte[]>();
 		public static (bool isDefault, byte[] bytes) GetPicture(PictureDefinition def)
 		{
-			lock (cache)
+			lock (cacheLocker)
 			{
 				if (cache.ContainsKey(def))
 					return (false, cache[def]);
@@ -67,7 +68,7 @@ namespace FileManager
 
 		public static byte[] GetPictureSynchronously(PictureDefinition def)
 		{
-			lock (cache)
+			lock (cacheLocker)
 			{
 				if (!cache.ContainsKey(def) || cache[def] == null)
 				{
@@ -104,7 +105,7 @@ namespace FileManager
 
 				var bytes = downloadBytes(def);
 				saveFile(def, bytes);
-				lock (cache)
+				lock (cacheLocker)
 					cache[def] = bytes;
 
 				PictureCached?.Invoke(nameof(PictureStorage), new PictureCachedEventArgs { Definition = def, Picture = bytes });