The scariest thing in that video? His wedding ring, that's a no-no for several reasons. Like you said, there is a LOT wrong in that video. I've been working with VFD's in my day job for years and videos like that one drive me nuts. You're exactly right, the quality and technology in some of the China drives is questionable, some are very good and some are a fire looking for a place to happen. One common fault I see in them is some mfgs cut corners and skip coating the boards. So you end up with a VFD that has naked solder traces and pins just waiting for dust to ingress and cause a failure. The enclosure type he's using (NEMA 1/2)is intended for mounting inside another enclosure for protection, not hanging on the wall behind the belt grinder. If you have ever seen sunlight shining through the dust those grinder throw off, it's amazing. Little tiny metal fish hooks floating around in the air.

The question I have is: Why would you try to repair a cheap VFD? Those things are just a throw away item.