Try this open each door one at a time and push down the switches you find that will be mounted to the interior lower door moldings.Try each one and see which one seems more stiff and try pushing it down many times fast to see if suddenly the interior lights go off and if they do go off then buy a switch from the dealership for a bout 15 bucks and remove the screw , unplug old switch , plug in new switch etc.
You can also try spraying soaking the switch heavily once you have the switches down and as they rise do that several times very rapidly that could fix the switch problem.But the dash switch for the interior lights can cause this too but you'd notice it in the switch too.
Hope that helps and best of luck.By the way you'd probably find parts like that for you car at the do it yourself auto wreckers quite cheap and you could grab several of the door switches and even two dash switches too for it quite cheap.