[sourdough]

I agree that it's more than likely condensation but I would also check all the seams if that is possible. If you can't raise the vent covers I would get a "good" dehumidifier and run in both the living area of the trailer and in the shower when showering.

The MaxxAir covers are worth every penny. No snow buildup, rain intrusion etc. and you can raise the vent for humid air to escape at any time.

We run a HiSense dehumidifier 24 hours a day when it is humid. It's pretty large (50 pint? 35 pint? - don't remember) and it's amazing how much water comes out of the air. At times the bathroom will still get a very small amount of condensation on the ceiling when we shower if we forget to open the vent. If we do open it we have no issues at all.