NextCloud: Added fix for idle loop

wiki/nextcloud.md

@@ -48,3 +48,38 @@ When using an [Android](/wiki/android.md) client problems may occur regarding up
 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.
+
+### Stuck with `Synchronizing files in local folder`
+
+When the NextCloud client is stuck with in an idle loop that is characterized by a status like
+`Synchronizing files in local folder` and/or `Syncing file 0 of <file-number>` where `<file-number>`
+is an arbitrarily large number of files.
+When checking the logging file in `~/.local/share/Nextcloudoud_sync.log` there won't be any obvious
+error messages.
+In fact there will only be a sync running without it finishing - unless interrupted manually.
+
+However, this problem can easily be fixed with the following steps.
+First the NextCloud instance which is stuck needs to be stopped.
+
+```sh
+nextcloud --quit
+```
+
+Afterward some files have to be removed.
+Firstly delete the cache at `~/.local/share/Nextcloud`.
+
+```sh
+rm -rf ~/.local/share/Nextcloud/*
+```
+
+And secondly remove the synchronization files in the NextCloud folder.
+`<nextcloud-folder>` is the placeholder for that.
+
+```sh
+rm -rf <nextcloud-folder>/.sync_*
+```
+
+Finally, restart NextCloud and the system should not be stuck anymore.
+Please note that after this steps a complete re-check of all files will be due.
+This however does not mean that all files will be downloaded or uploaded again.
+They will just be checked and only if the local version differs will they be synchronized.