What grounds did you check?

Are the fenders grounded to the body?

The 544 has few if any ground wires.

Each item from the bulb holder must have a good connection to each other part until you get to the grounded side of the battery.

I have seen several posts by people who paint some parts then have strange electrical problems.

I got my best lesson when one of the license plate lights did not work.

I found that a clip on the bulb socket must ground to the bumperette, which must ground to the bumper, ditto to the bumper bracket, ditto to the body.

All body parts that hold electrical equipment must be electrically connected to every other part.

One of my rules of trouble shooting is - 'What just happened before the problem arose?'

Your fenders got painted.