Unfortunately that did not help.
I’m quite confused now:
I’ve deleted the files containing the old versions of my plugin and recreated the extension package. Now I have the correct version of my file in these folders: local/lib/check_mk (of course) and var/check_mk/site_configs/<satellite name>/local/lib/check_mk. Obviously the satellite-specific files reside in a different directory than the old versions I’ve deleted before. It might be the case that these files existed even before the deletions, unfortunately I didn’t check.
Also I’ve confirmed that the correct version got replicated to the satellites (into folder local/lib/check_mk)
But now the check does not work any more at all. CheckMk reports for the existing services “no matching plugin found” and the service discovery does not show them any more.
So it boils down to the question:
How do the folders local/lib/check_mk and local/lib/python3/cmk relate to each other? Obviously checks only work when they reside in the latter folder while I install them to the first. What triggers them to be copied?