Glitching out and mosfet overheating.

You have magic hands!

Try cleaning the flux. I don't really have any other ideas except to change the crystal circuitry (load caps and crystal).

Toothbrush and alcohol. Not your current one, an old one is best.

Please avoid water. No acetone under any circumstances.

I must be magic too! I just did some experiments on my Modular Rev. 3 board and it seems Phil is right - my body passes enough current to really mess things up if I do the 2 handed touch. Right hand touching the tab of the MOSFET, left hand poking around. When I touched near the crystal the circuit crashed much like in your video. In addition to flashing random numbers and then blanking out, it came back up doing an HV calibration and the ESP module had forgotten my time server config. Mayhem. It appears there was no permanent damage - just blew it's mind temporarily.

Conclusion: finger poking bad.

I'm unclear as to whether your clock glitches out only when you are touching it or whether it does it on its own sometimes. If it's doing it on its own I'd recommend getting a new crystal and maybe even a new controller chip from Ian. There was another thread a while ago where a bad crystal was suspected. The thread ended without follow-up so I'm not sure what the solution ended up being.

Flux removal is still highly recommended but not quite as much of a priority now. I don't know how effective dish soap & water would be. If you try it use distilled water, readily available at the food market, and try to keep it off the component side of the board. Better would be to get a can of flux remover if you can. Here in the USA it's still legal, I have bought it at local electronics shops and at Fry's.

Okay, I'll defer to Ian on this one - no water. I've used distilled water as part of my routine for getting old dull looking copper clad perf boards ready for starting a build, but I'm not so sure I ever tried it on a populated board.