JabRef 5.0 synchronises updates to old postgres DB but not adding new entries

Dear JabRef team,

We used JabRef quite a lot and the last stable version we had was 4.3 which ran without issues (a bit slow in connecting but it worked! ;-)). Since the latest update to V 5.0 we can’t add new entries anymore.

The Shared database connection to our postgres database works fine. Using same settings, it connects now much, much faster than any 4.x version! For that, well done guys!

PROBLEM: It brings up all our old entries and we can update them. Checking parallel using PgAdmin and seeing the updates in the fields nearly instantly. So far so good!

BUT: New entries are not added anymore and synchronised. Any idea why that is and what can be done to get it working again?