NextCloud: Added Android colon Bug

wiki/nextcloud.md

@@ -5,7 +5,7 @@ NextCloud is a free and open source client-server cloud-service.
 ## Setup
 
 The software can be setup via [Docker](/wiki/docker.md) with the
-[nextcloud image](/wiki/docker/nextcloud.md).
+[NextCloud image](/wiki/docker/nextcloud.md).
 
 When using NextCloud with a specific nginx configuration you have to append
 `'overwriteprotocol' => 'https',` to your `config/config.html`.
@@ -26,3 +26,25 @@ used for another server or to nest data from two or more servers within each oth
 This however can be conveniently avoided by using symbolic links
 (for example [symbolic links](/wiki/linux/shell.md#symbolic-links-using-ln) in
 [Linux](/wiki/linux.md)), which are not by default synchronized to NextCloud.
+
+## Troubleshooting 
+
+This section will focus on errors and the fixing of errors of NextCloud.
+
+### `Error occurred while downloading files` on Android Clients
+
+When using [Android](/wiki/android.md) clients for NextCloud the error `Error occurred while
+downloading files` can occur.
+This error can especially show up when a file or a directory contains a colon (`:`).
+[Android](/wiki/android.md) might display them correctly but has problems with downloading and
+displaying them which seems to be a problem with file handling and the conversion of file names.
+Most notably this error is not reproducible with the [Linux](/wiki/linux.md) or
+[Windows](/wiki/windows.md) or the web interface.
+Simply renaming files and folders to not include colons fixes the problems most of the time.
+
+### Problem Uploading Files on Android Clients
+
+When using an [Android](/wiki/android.md) client problems may occur regarding uploading files.
+Most of the time no error messages are given but the error can be caused by a colon (`:`) and be
+similar to the [previous section](#error-occurred-while-downloading-files-on-android-clients).
+Simply renaming files and folders to not include colons fixes the problems most of the time.