Internal server error from nothing

Hello, suddently my nextcloud install started giving this error.
nextcloud.log is riddled with errors like:

Am I right, that you’ve enabled the theming app? If yes, try to disable the app.

It was alredy enabled one week before this happens today…
It was disable already (dunno why) but enabling it did no change.

It is nice that it has been enabled a week before, but please disable it and test access again!

The error persists after disabling Theming app.

Have you restarted the web server and your browser?

Yes, the entire VM.

Then I would expect other messages being logged when you try to login to Nextcloud.
BTW, you didn’t provide any information about your environment, which software versions you are using nor have you provided a step-by-step description how to reproduce the problem. This makes it difficult to cross check if any similar problems have already been reported in the past.

Sorry, i have nextcloud snap installed on ubuntu 18.04.
Here is full log:

It must be related to auto refresh from snap to latest version:

Ok, i got it working again thru sudo snap revert nextcloud command. It was due v.18 snap automatic upgrade.