Presumably it was the tape that degraded over the decades (perhaps stuffed in a box, moved from house to house, thought of as junk until they had the idea to post it on the internet)
I said this upstream, but I have clear memories of borrowing tapes of stuff people had recorded off their tv in the 90s and having exactly these kinds of glitches. I think we're seeing the difference between a professionally recorded vhs and a home system that someone just learned how to use.
The vertical hold going as in the featured article was more of a 60s/70s thing in my memory.