Also I don’t have files icmpsender and icmpreceiver anywhere on my system, so I suspect they only apply to checkmk core and not the free RAW edition.
But I am encountering exactly the same issue by the OP at the forum post below where I can ping the target host(s), but check_icmp is returning critical for the same host(s) (when I execute it from the shell).
So what I have done is to change the “Host Monitoring Rules/Host Check Command” to “TCP Connect” (port 6556) so now all the hosts are back UP. But would definitely like to fix the check_ping issue.