Problems adding folders to my desktop client

system is Mac OS Big Sure, 11.6, latest version of OC desktop client

During the sync I received an error message and a hint, asking me to remove the sync folder and add it again as it was used in a different account as well (what was not true).

But I removed all folders from the client, tried to add them again. Received a new error message.

“The folder /user/…” is used in a folder sync connection! Please chose another one"

which was not the case.

So I firstly deleted the user account from the desktop app and added it again. Same error message.

Then I de-installed the app including all config files, made a fresh installation.

Same error message as before. I still can not add any folder to the client.

Is there any specific file I need to delete or any flag I need to change? How can I add my sync folders again?

Thanks for your help

Check this comment:
https://github.com/owncloud/client/issues/9110#issuecomment-933209508

somehow what I expected, but not able to locate the sync.db files. Where are the located?

OK, found the files, deleted them, so that there is no _sync file remaining (not even the latest) but not working → same error message as before