maybe found it… running the command that shows errors in npcd.log shows
HiRes.c: loadable library and perl binaries are mismatched (got handshake key 0xce00080, needed 0xed00080)
while updating checkmk we updated also what was pending on the linux system, perl is now 5.32.1 as opposed to 5.28.1: is that the problem ?
/usr/local/lib/x86_64-linux-gnu/perl/5.32.1