The repro steps in your OP did not conjure the same bug as seen from my post. RE: simplified category styles post.
I start that video, scroll down, the video stops. I scroll back up, press play anew, let it run a bit then scroll up; it stops. Intended behavior. I am on latest Chrome/Windows 10.
So, this narrows down to videos that start from a spot specified in the URL.
After some experimenting, I’ve updated the repro steps. Its more tied to the post which contains the video, not the video itself.
Keep a tiny bit of that video’s post onscreen as you scroll around, and the video will reload every time the URL updates. Once the post goes offscreen, the video stops.
As for it stopping when offscreen: that’s the result of our cloaking, which tries to save memory by unloading things as they scroll off. We might be able to increase the threshold before this happens, or perhaps add a check to see if there’s a video playing, but I think it’s less serious of a bug.