Inside ceiling lights not working - do I have a short?

Not a short as that would blow a fuse. You have an intermittent open circuit.

Popups sometimes have some kind of switch to prevent the overhead lights from working with the top down. The Palomino my in-laws had used a plunger switch under the flip-over sink. Sometimes the sink would land on something and not fully push the switch.

It’s also possibly just a loose or broken wire since the wires to the ceiling lights have to move up and down with the top.

Looks like Coleman uses the galley kill switch.