I have basic scope knowledge... essentially, plugging in a signal and looking for that signal in a circuit, and an understanding of how to measure that basic signal based on the size/volt/time settings. Beyond that, none. I have a small Siglent digital scope but I've been looking for a smaller analog one that wasn't too expensive for awhile, just because I like them.
This seems to happen at any setting on the time scale but it's easiest to see when the wave is spread across the screen somewhat as in the video. I don't think the auto/manual trigger switch made any difference but I'd need to double check to say for certain.
I forgot to mention that when I got it, it was having trouble getting the trace up but I was able to narrow this down to a dirty switch for the component tester on/off. I also tried cleaning the switches and vernier control for the time dial, that helped eliminate some noise when switching (though it was working at that point) and left me with only this repeating strobe-like effect that you see in the video.