Years ago, I lucked into a collection of multiple RZ and RB bodies, multiple lenses, and accessories for only $700. Because of the electronic shutters, I was ready to keep the best of the RZ equipment and sell all the rest.
My repairman talked me into keeping the RB equipment instead, given his description of the internal complexity and build quality of RZ systems. I followed his advice and kept an RB67 Pro S system. I also had him do a CLA on that camera. The CLA was a good idea, based on what I've since heard about these older cameras.
I never did have a problem with that RB67 Pro S camera. It's also the case that I never used it.