I had an issues similar to this on my 444 when I replaced the actual blinker sockets with new ones, though my issue occurred on only one side of the car. Turned out the connection of the ground wire to the socket itself (a horrible, bullet-style plug) was loose on the front left blinker. I secured that at the light socket, and the issue went away.

Since those were most definitely removed for fender painting, either front or rear, I would pull those from their rubber mounts and make sure all the wires are tight at the sockets themselves.