Nope, never needed to take one apart yet. I have had a couple of blank frames recently though, really need to work out whether they were a lens or body problem. There seems little pattern to them - had one on the second frame of a film (the rest were fine) and the other on the penultimate frame (the rest were fine, even the final one). I suspect it's a case of gear that needs more exercise.
The Bronica lenses have the shutter mechanism built in, so I wouldn't fancy opening one up.
That's what i am thinking as well - I did give it a try (even with the right screwdrivers) and I met some resistance - they put some reasonably decent loctite on those screws!