I think on any trailer, regardless of who built it, the AC is going to be potential trouble spot since its a somewhat heavy piece equipment sitting on a hole in the roof. So if it's not sealed properly its going to leak and when water gets inside it can cause the roof to start to sag making the problem even worse.
This is also a maintenance item. Every year the caulking should be checked to make sure it's still in good shape. Over time it degrades with exposure to weather and vibration from moving. So, like anything, if the maintennace hasn't been kept up there is a potential for problems.
Check out the seals around the AC, and look for any sagging in the roof. If it looks OK you are probably fine. Good luck!
2011 Chevy Silverado Crew Cab 4X4
2009 210 WBS