Oracle NMDA backup failing since upgrade

Hello all,

we updated NW and NMDA from 19.4 to 19.8.0.3 on Linux RHEL 7.9 with Oracle 12.1.0. Now the Oracle NMDA backups are failing. This error is thrown during the attempt: 

NULL no output found in /nsr/apps/tmp/nsrdasv.1702555865.6102.vgenU1
Exiting with error: 
Could not connect to the Oracle database ORACLE_PROD at /opt/oracle/product/12.1.0/dbhome_2
oracle_server:     Could not connect to the Oracle database ORACLE_PROD at /opt/oracle/product/12.1.0/dbhome_2

 33058:nsrdasv: Could not connect to the Oracle database ORACLE_PROD at /opt/oracle/product/12.1.0/dbhome_2

Also the configuration wizard throws this error when trying to check the config:

"Unable to perform OS authentication by using the OS user 'oracle' and Oracle instance SID 'ORACLE_PROD '. Verify the user credentials."

But the user oracle user does not need a password and has sufficient rights. We downgraded to 19.4 again and the backup ended successfully again. But actually no configuration by wizard is possible anymore.

We checked a lot if things as reconfiguring and recreating the client, deleting nsr peer info. Filesystem backup is also ok.

NW server is on Rocky Linux 9.2 with 19.8.0.3

Any ideas?

Thanks in advance.

best regards