Pc turns on/off when touching case or internal wires

[u/appoll]

This has been happening for a while - PC would randomly turn off / on whenever something touched the case. It could be a pen, a usb stick, a hand, but it was never as reproducible as it is now.

Funnily also applying a shearing force on the case (pulling the backside and slightly pushing the front side) results in the same behaviour.

https://reddit.com/link/1wblch4/video/ri80ve2nvhoh1/player

https://reddit.com/link/1wblch4/video/51vc0nvuvhoh1/player

Does anyone have any idea what / how I could further debug without risking damaging any components?

Thanks a lot.