Is your system gen-locked?
I’m wondering if I feed the Decklink black burst it might make a difference. For me, it seems to be triggered by audio only clips. If I load an audio-only clip in the source monitor, no video is output at all…not even black…I’m wondering if that causes loss of sync.
Desktop Video 9.0, the video is stable…even on an audio-only clip…I just lock up when I try to scrub with caps lock on.