Every model camper is probably wired differently.
I took a look at how my camper is wired and can see that if the ground connection in the fuse box were open, it would disconnect ground to the running lights also. That would also cause any 12V device to fail, not just interior lights.
The ground bus can still be connected to the converter ground, so all 12V items would work if connected to shore power except running lights.
All my running and tail light grounds tie together and then run to the fuse box ground buss, while interior lights have two separate ground returns.
The battery, TV, and converter have separate ground wires to the buss. For both running lights and interior lights to fail at the same time would require that two wires fail at the same time.
Possible both the battery ground (probably a #6 AWG) and the TV ground (probably a #10 AWG) are under the same screw on the ground buss???? Pure speculation.
