Hello Bernhard,
we might get closer in finding the bug if you could upload your complete database catalog for that user (includes all database object definitions, but not the data).
Doing so would mean to extract the database catalog via the 'loadercli' command line tool:
1. loadercli -d <yourdatabase> -u schemauser,password
2. export user catalog outstream file '<someFileName>'
And here is a valid upload link:
https://mdocs.sap.com/mcm/public/v1/open?shr=I0BR_ij2xY7tDHqU6KShrP9eCdVSMwiBLK-Kxflo-fY
Regards,
Thorsten