Just moved into a 1940s/50s house, very old wiring. I noticed all the outlets in one room indicate reverse polarity when tested with a basic outlet tester. I took one out to examine the wiring, and it seems to be wired correctly.
I then noticed that while the outlet was out of the receptacle, the tester indicated correct installation (hadn't actually done anything with the wires yet). These outlets are ungrounded, with a single neutral and single hot wire. Touching one of the outlet screws to the receptacle causes the tester to flip back to 'reverse hot/neu', pulling it back away returns the tester to correct installation.
Ideas why? Ideas how to fix?