For many month I had few Group Devices configured:
Suddenly I noticed they are disappeared (except for one) from the Devices page:
All they are still assessable to RM and even briefly appeared on the Device page when this page is refreshed.
I guess, I still can use these groups in RM but why they are not showing on the Devices page?
I am not sure when exactly they became invisible (definitely after migration to C8) since everything seems to be still working just fine.