Yes I have the same problem with my camper.
The factory spec is a 8000 btu side wall AC for my small cabin size. But my unit has an upgraded 13500 btu unit. So unless it's VERY HOT outside, it quickly cools the cabin before it can dehumidify it.
Two fixes I've found.
1. Compressor dehumidifier, I bought a 90 pint Frigidaire unit. Works great and fast.
OR
2. Small space heater set on medium. Keeps the air warm a bit longer so the AC can draw off the moisture.
If I'm on generator I'll run the dehumidifier it works better and faster, and takes less power.
If camping with included electric, I'll run the heater.