Voltage at the light socket of my ceiling fan is 138 volts

I have a ceiling fan in my office that's been there for about 10 years. The fan part has always worked perfectly but the light has always been dim. It hasn't bothered me until recently when I reconfigured the room and wanted that light to be brighter.

The fan has a combo fan/light wall control, I've never used a remote control with it and as far as I know there is no remote receiver unit in the fan but I'm not 100% sure, I didn't install it.

I tried changing bulbs, no effect, I have a Lutron wall control, I read that these can give out over time so I replaced that too, no effect.

I got a multimeter and checked the voltage at the 2 wires coming into the light socket and it reads 137-138 volts. I double and triple checked this. The multimeter is on the 200V setting.

I plugged the multimeter into 2 different electrical sockets and it read 120 volts.

How can I possibly have 138 volts to the light socket? I could understand if the voltage was low because of a bad wattage limiter or something. But how can it be high?

This is a Modern Fan Company ceiling fan.