After updating, now the second time, from 12.0.3 to 12.0.3 (before from 12.0.1 to 12.0.2 the same problem) I got a “Content-Encoding-Error” and no access to the Nextcloud 
The server is running on a LAMP System (embedded Linux, QNap Server) and I started the update with the updater in the admin section. The update run til the end, but when I then came back to the Nextcloud URL I only got the Content-Encoding-Error…
…any ideas?!
Like this it is difficult. Normally if you configured everything, it should change that much from version to version. How did you solve it from 12.0.1 to 12.0.2?
Haven’t seen this problem so often, so it could be related to the embedded Linux. Therefore, it is harder to find people here with deeper insight than regular distributions.
The problem from 12.0.1 to 12.0.2 was the same as updating from 12.0.2 to 12.0.3 …with the 12.0.2- run I did a complete new installation …but that could not be the solution!
What worked was the update with the ssh console:
Blockquote
/etc/init.d/Qthttpd.sh stop
cd /nextcloud/
sudo -u httpdusr /mnt/ext/opt/apache/bin/php occ upgrade
/etc/init.d/Qthttpd.sh start
I never had such problems with updating while using “owncloud” on the same QNap server?! Even if it is an embedded Linux it is a normal Apache/ MySql/PHP machine?!
It’s probably similar. They sometimes have specific configurations, updates and security fixes come later (or only during the support cycle) and there are less people using it. On a default Linux, everybody can take an image and spin it up in a virtual machine. In your case, it would need someone with the same system.
Unless you know the reason behind this problem, it is impossible to say if it would happen on ownCloud. Both projects are still very similar in required modules.
I found one pull request that directly mentions encoding which was merged into 12.0.3:
Make a backup, keep the original files, then you can try to undo these changes if that solves your problem. If that doesn’t work, you could file a bug report on Issues · nextcloud/server · GitHub, perhaps they can help your to tell at what point the code produces the error and which part of the configuration could be responsible.