Mini converter flickering lines and jitter

I have an HDMI to SDI mini convertor going from an iMac into an ATEM production studio 4K. 4 days out of 5 it works fine but occasionally when we boot up there are flickering green horizontal lines and jittery image. Resetting doesn’t seem to help once it begins. It’s just goes away by itself over time.

https://en.wikipedia.org/wiki/Interlaced_video

https://en.wikipedia.org/wiki/Interlaced_video

Not at all, Sound more like SDI errors. ( Jitter and lines are often CRC errors in the video data. )

Check your cables.