The Bessa R4M slide off my car front seat thanks to someone who had braked in front of me. It had the 21mm f4 Skopar (screw mount) lens attached with the lens cap on and I didn't notice any issue.
I now notice that the rangefinder is out of alignment. I can see vertical lines align fine, but horizontal lines stay out of alignment even at infinity. I also tried another lens and the same issue happens....
I found several threads here about this topic but can't find the reference document on http://www.arransalerno.com
to open it up and tighten some screws. (That website is down).