Yes I'm aware of that. The problem was the mount tried to perform a flip (alternatively stop the tracking, depending on your choice in the hand controller) exactly at the meridian, even if it was set to do so at meridian + 5 degrees.
If the mount wants to perform a flip before the controller software (in my case Stellarmate) it will do so and the imaging sequence will abort and the rest of the unattended imaging session is ruined.
I was in contact with iOptron support. They recommended me to upgrade the mount firmware.
So I upgraded from 210105 -> 210605 and can now confirm that it works fine with Stellarmate v1.6.1
So it turned out to be a bug in the mount firmware.
No matter what controller software you use, you should do this firmware upgrade or the meridian flip will be uncertain.
Hope this helps any CEM40/45 user out there!
Cheers, // Åke