Justin, it's not obvious from the forum name, but we are focused on all-molded, "egg"-type, fiberglass trailers (Scamp, Casita
, and similar). Ours don't have edges or roof seams, so the issues are different.
If there is no leak, it is possible the moisture could be condensation. Maintaining ventilation in cool, humid conditions helps with that.
But I do think you have to consider the possibility the roof seam is leaking somewhere. They are the bane of conventionally-constructed RVs and the reason many of us have chosen the molded fiberglass alternative.
For finding and fixing seam leaks
, you might get more and better information on s general RV forum such as iRV2.com.