Service Unavailable 503 / 500

Hi,
already posted a Thread here, which gives some Information but i didn’t found a Solution yet.

Problem: still got few Errors in Backend, regardless if i want to upload a new Images for Theming, or Change Passwort within the encryption Module or if i want to view some Files which was uploaded via open shared Link.
Previews of existing files wont show up. Seems like everything is brooken.

Last big task:

  • moved NC12 to another NC12 from debian to ubuntu. (with reading doc very carefully)
  • repair command went good, filecache deleted, enabled and discabled some things,
  • rescan all files went good.

This seems similar as my case: Photos uploaded via public upload not accessible (with encryption module) - #10 by Claas
but i already have latest NC.

No i have some new Screenshots attached here.

System:
NC v12.0 Stable
PHP Version: 7.0.18
mysql Version: 5.7.18
Ubuntu 5.4.0-6ubuntu1~16.04.4

Does anyone can help me?