We camp in the fall also. Mid Sept. ---- mid Oct. We are without electric (dry camping)
When it gets cold, we found the same thing, condensation!
What we found that works for us, is in the morning when we left camp we opened the windows and let the air move thru. It was always dried out when we came back at noon. At night we had one window on each end of the rig cracked open and the overhead vent in the bathroom open about 1in. We have an Olympian Wave 6 catalytic heater we use. If it was cold in the morning when we left, we just let run. I think it ran for 48 hrs. one time without being shut off. Nice heater and very economical to run.
With the thin walls and what little insulation they put in, camping in that temp is going to cause condensation. I had the ceiling in the slide open running some electric wires, and all that is up there is a weak 1in. of insulation "floating" around.
All you can do is make sure you get it dried up right away. Keep air moving!!!!
We also kept our cupboard doors open and closet doors open. Keep the mattress and pillows off the wall.