Different temps and humidity conditions between the inside and outside of the camper is the culprit. Venting the tent ends (even in the winter) can help. Had the same problem with my pop-up. In my case, the inside being warmer combined with the natural humidity from people inside sleeping and the colder outside temps caused major condensation in the tent ends. We learned early on to vent the tops of the ends and any other zippers that could be vented at the top. I assume in your case it's body heat-to-outside temperature that's causing the condensation. Other than venting, not sure what else can be done.
2013 Jayco Eagle 328 RLTS
2013 Ford F350 6.7L 4x4 CCLB W/Air Lift air bags
2002 Coleman Bayside Elite (traded)
Me, Momma and Charles (RIP buddy)
And introducing Sofie!! ;)