Still some infrequent and minor twitching on my SE's video, so I took the final step* and recapped its ASTEC power supply. There was one small area that looked like cap ooze had been there. Now, the suspense begins.. either the video is now spot on, or after a long while it'll do it again. (* things like the flyback etc. are just out of my league, and the problem is too minor to risk those )