Strange Issue with SNES 5V Regulators

So I have about 5 SNES Motherboards, all with the same issue.

Each non-working board displays a black screen, but powers On. I can read the 5V regulators with a Multimeter, and they read about 12V as opposed to 5v. The strange thing is, each 5V regulator is actually GOOD. I can take them out, and they will read 5V. Same goes if I swap it with a brand new 7805 5V Regulator, they will read 5V once removed from the System, but as soon as they are put back in to the non-working System, they read 12V.

My SNES's that work fine, all read 5V when I test them. So, I'm trying to figure out what could cause that problem, so that less resistance is getting through to the PCB, too much Voltage seems to be the issue, but the issue is not with the 5V Regulator. I'm using a 3rd Party Power Supply, but they work fine with my working SNES systems. Anybody know what might cause this, or where to look? Something must be attached directly to the Regulator (ODB?) causing a failure... anybody have any ideas? Thanks