"I remeasured the outlet. Here are the readings that I got:
Ground to neutral slot equals 121.6ground to hot slot equals 3.6
neutral to hot equals 124.6Hot to neutral equals 124.6"
- Hot to Neutral 124.6 (let's call Hot - Line .. more typical term)
- Ground to Neutral Slot 121.6- Ground to Line Slot 3.6
I assume this measurement was made with almost everything turned off?
Hot-Neutral is 124.6 ... or about the same as Ground-Neutral + Ground-Line. With a noise-free reading, (G/N) + (G/L) should approximately equal the source voltage at your electrical panel AND and should be higher than what you measure L-N at the outlet.
(G/N) + (G/L) = 125.2 - Or perhaps the voltage at the panel(L-N) = 124.6 - Or the voltage after all the drop(G/N) + (G/L) - (L-N) = 0.6
However, as stated G-N should be close to 0, but often is not due to drops in the wires (and noisy measurements). Given you have 3.6 with what appears a very small drop on L-N, that suggests either a noisy measurement (possible), OR, it could be a faulty ground connection on that line. Given the wiring issue already noted (and DIY nature), I would be investigating the ground integrity. Fortunately, you can do this yourself.
1) Turn the breaker off!!2) Wait 30 seconds (any leakage from capacitors in power supplies)3) Ensure the L-N, G-L and G-N voltage is 0. I am expecting G-N is 0, but if it is not really close with power disconnected, that is an interesting result. If it is no 0 or really close, DO NOT CONTINUE!
4) Repeat step 3! ... you really need to be sure.5) Put your multi-meter on the ohms setting.6) Measure the resistance between the Ground and the Neutral (the ones that was measuring 3.6 volts). It should be <1 ohm with a good contact between the probes and the socket.