
They’re $15…
Buy one and see if it fixes it.
However, I don’t want to take for granted that you’ve moved the plug to a different outlet and tested it there, along with testing the outlet it’s normally plugged into.
It’s probably a bad supply, but it takes 2 minutes to follow thru with the rest of trouble shooting.
I identify that supply reads bad in different outlets, and something that works fine, still works fin in the problematic one.



















I haven’t dealt with electrical engineering in a decade, but it sounds like you isolated the problem to the supply. Assuming you meant it was reading normally at outlets, but the supply read wrong at multiple outlets.
Definitely do not try to do anything to fix it. It’s already broke and not worth the risk.
So order the new one, don’t plug the old back in. And maybe someone who knows more can explain how the original broke.
It’s good to want to understand this stuff, but it’s never worth rolling the dice on repairing something as cheap and constantly in use as this. Probably the biggest lesson with electrical shit is “don’t cut corners”.