I had a similar problem with mine. It has the factory turn signals. The brake lights run through the turn signal switch and mine will not center exactly after cancelling. Just a tiny bit off and the brake light on one side or the other wont function. I rigged up some small indicator lights mounted under the dash and wired them to the brake lights so I can tell if they are operating and make a small adjustment to the turn signal arm if needed to center the switch. Until I rebuild the actuator arm thats dragging this works for me. Also, I noticed with my lights on, one side was brighter than the other. I found the brake and running light leads were switched at the taillight. The brake and turn signal filament in the bulb is brighter than the other one when energized. I hope this helps.

Jeff

"Do not walk behind me, for I may not lead. Do not walk ahead of me, for I may not follow. Do not walk beside me either. Just leave me alone, you're starting to freak me out."

1957 GMC 150