Animation and Video Desynced after saving and closing

I was having some trouble durring which a frame I was drawing on wasn't updating until you left it and came back to it. I saved and quit in order to hopefully resolve the issue, but a new one was created instead.

I have a video file in the background which i am drawing over.

Forgive the "phone recording screen" thing, the original i recorded to quickly show a friend, I hadn't anticipated sharing it.

Here's the animation Synced:

and here's the animation Desynced after saving and closing:

Is there anything i did to cause this? to my knowledge i did nothing. Can I fix it? thank you for your help.