Agreed that it is most likely the safety switch or the ground wire. Check the ground first and then the switch. We had to replace our switch when it exhibited similar symptoms to what you described. When you find the switch, you can test it by bypassing the switch with a jumper wire. Ours ultimately failed on a camping trip so I had to bypass it while we camped. Just be sure you remove the jumper wire before lowering the roof as the lights, if left on, will burn a hole in the tenting material and could cause a fire.
Depending on your layout, the switch could be located one of the corners or if you have a swing-over galley, on the counter where the galley rests when popped up. That is where ours is located.
If you have a loose wire somewhere, you can usually narrow it down by just jiggling the wiring while someone watches the lights. Jiggle a wire and the lights flash tells you that you are on the right track.
