Hi @blazej.s
But this documentation is from “Last modified on 16-Sep-2019”.
Just because the documentation is from 2019 doesn’t make it wrong. It’s still true.
From one and a half year, we had mixed version but in range of 1.6, and everything worked fine
If I understand you correctly, previously you were using different patch level (p… ) of the 1.6. That (normally) works, as @Man-in-Black already quoted. So mixing 1.6p17 and 1.6p12 would normally work.
But mixing two different major versions of Checkmk (so a 1.6 and a 2.0) will not work.