Exporting .mov file glitching and gaps in color card?

I was trying to export my file as a .mov and for some reason every time I play the video it flickers, as in the screen goes back and forth from black to the animation. I think it’s probably because there are weird gaps in the color card, but it doesn’t let me extend it. Before exporting the first time it requesting some weird codec thing to and I pressed yes without knowing what it is. Does anyone know how I can fix this? Thank you.

First of all try switching to ‘software only’ rendering. under > File menu > Project Settings > General > Renderer pull down menu. If you already have this as ‘software only’ try one of the other GPU acceleration options. Then do a test export.