Sorry, we updated our single-site from 2.0.0p28 to checkmk 2.1.0p11 yesterday. The Dashboard error was still there, then I reread the linked manual page in the Error message and fixed it.
We only had the monitoring server added as “localhost”. Added the monitoring server as “hostname” too and the error went away.
Maybe the real problem is the manual (should tell this requirement more clearly).
BTW: “Percentage of total service problems” didn’t show the error in checkmk 2.1.0p11 before adding the monitoring server with hostname.
UPDATE: Ok, this did not fix it… i am gonna test your file.