Yes, the are RRD files under ~/var/pnp4nagios/perfdata and under ~/var/check_mk/rrd.
The error messages are similar to
2023-05-26 10:58:27 [4] [main] [RRD helper 1643] [log] Error creating RRD for pnp_multiple;XXX;Interface port-channel434;outdisc;0: Tried to create /opt/omd/sites/mysite/var/pnp4nagios/perfdata/XXX/Interface_port-channel434_outdisc.rrd, but this RRD exists.
And yes, that RRD exists and its timestamp is about 2 months ago
-rw-r--r--. 1 mysite mysite 384952 Mar 21 03:28 Interface_port-channel434_outnucast.rrd
This site was updated from 1.6.0.p28 to 2.0.0p27.