Cannot set timezone for UTC properties

After my change from Nextcloud version 14 back to version 13 I get following message from Android Sync App DAVdroid: Cannot set timezone for UTC properties

These are the data set in the Nextcloud installation:

Calendar app: timezone Europe/Vienna
config.php:   'logtimezone' => 'UTC'

Is this is a problem in the MySQL database? What can I do?

I got an answer from the developer of DAVdroid. This is obviously a problem of Android 8. More information can be found in their forum.