Various errors: Theme failed to load, Propfind failed and ERR_INCOMPLETE_CHUNKED_ENCODING for SSE service.

## Describe the bug
All functionality that I use, seems to work, so its not like I can pinpoint an exact bug, but I assume these errors and warnings in the console shouldn't happen anyways.

## Steps to reproduce
1. Run ocis 5.0.9 in docker
2. Upgrade according to the guide https://doc.owncloud.com/ocis/next/migration/upgrading_5.0.x_7.0.0.html
3. Start ocis 7.0.0

## Expected behavior
No errors and warnings in the console

## Actual behavior
These following errors and warnings appear:

Comes on login

Comes when navigating to preferences

Comes periodically.

## Setup
Started with docker compose

## Additional context
The switching between themes work well.