Bitbucket Server login issues

Hello there,
we have a little issue with the login process on bitbucket server and we may need a little tip where to look further.
When accessing the drone server web link and logging in bitbucket is asking for authorization each time after a user is logging in again or the drone server is restarted. Each time a new drone incoming application is created in the users account. Is this normal behavior? Our previous test with a gitea installation isn’t doing this. Executing builds is working fine.

Also under “outgoing authorizations” the application isnt authorized. When ckicking on “Authorize” we are only getting this:

Authentication failed!

An error occurred while trying to obtain an access token. For application link "Drone (7808c394-1f98-32c6-911f-322b7631852a) generic"

The drone debug log doesnt show anything at all.

Does someone have a little tip if this is all “normal” or where to look further?