So I've been having this problem with one of my technos. The shutter on one side would stick. I thought it might be a bad motor so I changed it out. It worked for a few minutes then started doing it again, but now everytime I use the fixture for more than five minutes it gets stuck moving back in an extremely outward angle. Here's a quick drawing of what I see from over top of the light with the head off (forgive my horrible paint skills) The red dot represent the end points of the back and forth of the shutter.
img187.imageshack.us/img187/4890/13365107jd8.gif
when I stop the shutter, put them back in place, it goes right back to it.
I know the trick for when the shutters are sticking together due to heat, so I know it's not that and there's no loose screws, but I've never had a techno that's done this and cant seem to figure out why its doing this