We will need to know what system of monitor you have. If the monitor itself is getting a trigger feed for a turn signal it switches to that side camera. If you have a stand alone camera switch then you need to focus on those connections. I would follow the advice above and clean all the contacts and let us know what results.
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7