You must have a 50 amp shore power service to the coach and have these appliances on separate legs. When you are using the generator the output is only 120vac and therefore both legs in the distribution panel are now tied together; putting both appliances on the same leg.
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