Thanks for the video(s). It really helps.
Wow. OK. That last set of symptoms is something else again. Never seen anything like that. The LED is blinking much more rapidly than for the usual connection error reports. It’s usually more like a 1/4 or 1/2 second cadence. What you’re seeing there seems much more ‘erratic’ and strange. Plus, the yellow color indicates bootloader mode, which AFAIK should never happen on its own, unless something is badly wrong.
I’m fresh out of ideas at the moment. It’s looking now to me like something may be physically wrong with your 'core, unfortunately.