Hi,
many thanks for answering!
Unfortunately, for those hosts this was not happening.
But! I have discovered the reason of strange behaviour!
I found that there were actually some Endpoints and Zones (corresponding to those hosts) created on Icinga Director (just under the banner not to do it, apparently someone didn’t resist the urge to try it!). After deleting them (through interface or : How to Delete Zone) all is working as expected!
Maybe that serves someone stuck as I was.
Greets!