Jabref error

[Wolfgang Engelmann]

Slightly OT

I use jabref as a reference manager for including literature in my lyx 
documents.
I get a very annoying error >
The library has been modified by another program
  and I don't know how to handle it.

I use
JabRef 5.6--2022-04-25--5c9d898
Linux 5.10.0-14-amd64 amd64

and according to a search in the internet this error should not occur in 
version 5.6 anymore.

Has somebody a solution? I tried various changes in the preferences, 
without success so far.

Wolfgang