Ultrastudio HD Mini shows grey lines on SDI B

I’m having the Ultrastudio HD Mini and the in- and output without keying are working great in 1080P50. But as soon as as I put on the internal or external keyer by the Livekey app the background becomes grey instead of black and there are vertical lines. When I set to 1080i the background gets green. I have connected the Ultrastudio SDI out B directly to a monitor for testing purposes so without any extra devices.

I bought a second unit but this unit has the same problem. Anyoune having a solution? I saw more people with the same problems in this forum but there was not a solution mentioned.

Edit: I’m on an Intel Mac with Monterey (2 Mabooks, both have this problem).

ARE U on windows or mac ? If Win , try caspar cg, for test ..

Sorry I forgot. I’m on an Intel Mac with Monterey. I have two MacBooks, both have the same problem.

Well, the problem is partially solved. The Ultrastudio works perfect in other applications but I only tested it with Blackmagic Media Express which doesn't work.