Playback issues with UltraStudio 4K mini

I have just updated my iMac to Big Sur, and updated to Blackmagic Desktop Video to 12.1
DaVinci 17.2.1 works perfect ... But ... I can scroll through footage both on the timeline and in the viewer, but as soon as I hit a play button it stops immediately and the program freeze.
When I disable the UltraStudio in preferences, it works fine, but of course no monitoring. I have send a ticket to Blackmagic support, but until now no answer. Anyone else with the same problem?
DaVinci 17.2.1 works perfect ... But ... I can scroll through footage both on the timeline and in the viewer, but as soon as I hit a play button it stops immediately and the program freeze.
When I disable the UltraStudio in preferences, it works fine, but of course no monitoring. I have send a ticket to Blackmagic support, but until now no answer. Anyone else with the same problem?