Citrix VDAs become frozen, show unregistered in Studio, and user sessions get disconnected

Hi together,
I have a hard problem that unfortunately I can not get solved.
I have a Citrix environment in version Virtual App and Desktop 7 1912 LTSR CU5 on Server 2019. I publish desktops and have installed on everything brokers the latest VDAs.
I use FSLogix in version 2.98440.42104.
Unfortunately it happens very often during the day that the Citrix servers freeze.
All user sessions are disconnected and the hosts are displayed in the studio as not registered.
A connection via RDP or otherwise is no longer possible.
But the server is still pingable.
I can only help myself by switching the VM off and on again.
But this is very frustrating.

Unfortunately I can't find a solution and hope that maybe one of you has an idea for me!

Thanks a lot in advance.