When I first took my Edge into the dealership (two months ago) to have them look at the camera problem, they told me the camera hadn't been activated and asked me if I had the camera replaced at some point. The camera wasn't replaced, and it had been working fine for a couple of years until recently. The tech did reactivate the camera and everything worked fine for a couple of weeks, then the guidelines and zoom stopped working again and the camera intermittently goes offline altogether.
Since the vehicle is out of warranty, it's going to cost $300+ for the camera replacement. Oi!
Incidentally, the problem started even before I had the 3.5.1 update applied.