Ye some of the weirdest issues I've fixed have been PSU related.

I had a PC come to me that would boot fine, but if you opened the CD drive it'd shut off instantly.

Used to repair PCs in the mid 90s. Had guy come in with right mouse button not working suddenly. Replaced mouse. No go. Replaced motherboard, CPU, RAM, reinstalled Windows. No go. Changed the PSU. Right mouse button worked.