I have heard of several circuit board failures with the EC series, but they are all very old now, and they were an early electronic camera.
Parts should be available for leaf shutter Bronicas for quite a while yet, as factory servicing has only just stopped, and there are good places like Koh's to get them repaired.

I have not heard of very many failures of the leaf shutter Bronicas, and most of those were not of the circuit boards, but were wiring and contacts. I have heard of some failures of the electronics in the lenses, though as the body does the timing I would think that's probably related to bad connections or contacts.

That said, I have had one ETR-Si body fail to time the shutter, and the circuit board in an AE-III finder fail. So it does happen. But the overall reputation for reliability for the leaf shutter Bronicas is quite good. I would not consider the presence of electronics in the camera body to be a reason to not buy one.