Hello Andreas,
npcd.log returns a long stream of
[08-31-2021 09:03:20] NPCD: ERROR: Executed command exits with return code '1'
[08-31-2021 09:03:20] NPCD: ERROR: Command line was '/omd/sites/watchdog_1_01/lib/pnp4nagios/process_perfdata.pl -n -c /omd/sites/watchdog_1_01/etc/pnp4nagios/process_perfdata.cfg -b /omd/sites/watchdog_1_01/var/pnp4nagios/spool//perfdata.1630363648'
rrdcached.log shows some errors just right at the restart of omd after upgrade and at the start of the server
2021-08-30 16:07:42 [3] journal_replay: /opt/omd/sites/watchdog_1_01/var/rrdcached/rrd.journal.1630335895.240174 : Permission denied (must not be user/group writable)
nagios.log doesn’t seem to contain any errors.