Seahub fails after downgrade from 8.0.2 to 7.1.5


I realized that the thumbnails are not working in 8.0.2 server on Ubuntu 20.04.
So I tried to downgrade to 7.1. using the in the 7.1. upgrade subfolder.
However, seahub fails to start without providing an error.
So I tried to re-upgrade to 8.0.2., but seahub is still failing to start.
How I can fix this?
The seahub.log shows no error?
I am getting nervous to fix my server.
Please help!
Kind regards,

I was able to fix it with the tips from “Seahub not starting”, sorry for double posting