We use Unreal as composting tool with Composure. We output the composure result using a Decklink Duo 2 card. As soon as we activate the Output, Mouse and Keyboard events are ignored every now and then. This results in the mouse not moving and keyboard keys not registering, oder being held down aritifically.
The problem is only the input events. The engine itself is running without issue continuously (no frame issues).
We tried with OBS Studios to isolate the issue. No problems here, so the capture card itself does not seem to be the Problem.
The issue is system wide as soon as the Output to the capture card is activated. Means, if Unreal runs in the background, the issue is still apparent everywhere.
We tried different settings for the Output asset (Blackmagic Media Output), tried different ports on the capture card itself and different settings via the setup software of Blackmagic.
The issue is reproduceable in a fresh project.