Hi Mike,
Be careful when working with lights mounted to aluminum skin campers. Often the aluminum is used as a ground for the lights. If the screws, metal frame of the light, and the camper skin do not make good conduct...poor, unreliable, or no lights 😞
A tip: Take about an inch of multistranded wire and skin all the insulation off of it. Put it into the hole in the camper wall and through the hole in the light, then put the light in place and run the screw in. Ideally about 1/8-1/4" will be left to wrap around the screw head, just be sure it doesn't touch your hot or bulb, just the grounding plate.
Of course you can seal it up, then. The wire helps the screw get a fresh bite and helps with grounding all around.
And, yes, good advice to check these. MOST of the screws I have pulled out on many campers and trailers are rusty :E (When cold outside, the screws will conduct the cold along its length inside the wall and if it is warm/humid enough, it can condense. (Same with your house insulation and wall sheathing, ref:thermal break)