Turn Signal problem

[Orence1]

I am re-assembling my 72 after a complete body shop make-over. My problem is the passenger side front turn signal. When I assembled the bumper with the signal it worked intermittently. Nothing doing now. I have double checked the bulbs and they are OK. I have power at the plug coming through the core support. The issue seems to be with the turn signal unit itself. I had the unit checked today and it does show continuity so logical assumption seems to be a ground issue. The bumper is painted on both sides and I painted the turn signal unit. Thinking that may have prevented a ground I cleaned the paint from both the unit and bumper where they make contact (two screws through the bumper) and still no luck. Has anybody had a similar issue and can provide me with a potential solution? Many thanks in advance.