My Citation Sprinter has a "switcher box" that all the cameras connect to. The switcher has one output that goes to the Axxera unit. The turn signal, backup send signals to the box so it sends the correct camera signal to the display. Mine was acting strange, intermittently I was getting "No Signal". I found the ground wire on the wiring harness to the "Switcher" was hanging on by a thread of wire and broke when I pulled it out of the dash. Since the power to each camera goes through the switcher, the bad ground was the cause of failure.
The company that made the Switcher is: Rear View Safety. https://www.rearviewsafety.com
A new harness was only a few bucks. Be sure to have the correct model number, if you call for parts. First time, they sent me a 5-wire harness, instead of a 6-wire harness.