Have you tried different controllers or are you working with the built-in programs/sound activated programs?
I know for a fact that a controller can play tricks with fixtures. I was using another controller prior to my Show Designer and it caused the active fixture's mirrors I was programing to sort of shake and twitch (Mighty Scans).
Also, did you try working on each fixture individually or all of them in a chain? If individually, does this problem persist in both individual and chain setups, or does it come and go depending on the setup?
Is this problem consistent or intermittent?
Sorry for asking so many questions. I have a rig of mighty scans myself and I'm interested in trying to help figure this out.
Best,
-Tech