I was trying to fasten the top screw on the power supply of my Ender 3, but it won't fasten. So, I took the screw out and found something like a little yellow ring stuck onto it. I think it broke because I may have over fastened it, but I didn't tighten too much... Is this the "thread" of the hole? Is it supposed to be so fragile?
Sounds like you've stripped the thread by overtorquing the fastener.
Your options are to use a slightly larger fastener and drill/tap the larger hole for that bigger thread. And don't confuse the screws next time you open this connector.
The little yellow ring might be a retainer so the screw is held captive in the part, or it could be a load spreading washer, or a soft area to soak up vibration and prevent buzzing/rattling and resonance.
