Not uncommon. Ours did the same on the Forester we had. That roof is just alulminum framed with block foam, with ducting cut out of it, which is unlike the typical trailer with batten insulation and small foam ducts. Rockwood / Flagstaff are similar in their constructions. One issue we had with ours, is the cold air leaking into the front cap, which told me the foam was everything but air tight. I kept noticing cold spots in the morning on the cap. I baffled off the duct at the end of each run, and that solved the issue. A lot of our air was leaking into the cap and wherever else it could.
A small dehumidifier will definitely cure any condensation inside the coach. We run one at 45% or so, and never have any condensation, summer or winter, hot or cold, showers or not. In a Forester / Sunseeker, a dehumidifier like ours might not be an option since you're already pressed for interior real estate.
John and Rebecca Dickson
Emma-7 / Little John-5 / Iva-1
Full Timing Again, Rev B
2013 Ford F-350 Lariat CC LB PSD
2015 SOB TT - With OC's Awning Poles (#8)
At least in Heaven, RVs will be perfect, and I won't have to keep fixing them.