Mine did that at the HDTV antennae crank. I discovered the rubber boot that goes over the coax cable wasn't pushed on all the way. I pushed it back in place and added some sealant for good measure.
I also found an exposed screw at the front cap that was missing sealant entirely. I put some Dicor on that.
And, the cover for my sewer vent was on very loose. (to check security I went to pull on it a bit and was like, "dang this this is about to come off!) I replaced the screw with one that fit better.
I also found that the sealant for the ladder was beginning to pull away from the metal tubes. (you had to look really close to see it) I put Dicor on that today as a matter of fact.
I woke up during a downpour a couple weeks ago and found a water trickle coming from the emer exit window frame and then running down the inside wall! Big mess, took a large bath towel to clean it all up. I used a ladder the next day and saw a couple small gaps in the sealant on the top bead of that same window. Put some GE 100% silicone II across the top and no leaks during heavy rains since.
Lots of headaches I suppose, but for the most part I consider myself fortunate to have found these early on. If my coach had carpeting, and this happened in storage, I can imagine how quickly it would have turned things to black mold.
Point being, a quick overview is probably not enough. When you can say that you ran your finger over every square inch of sealant on your roof, and looked over every roof-mounted component with a critical eye for gaps and such, then you should have your answer.
Hopefully it is something simple rather than your air conditioner gasket. Even that doesn't look all too difficult in videos.
2015 Thor Challenger 37ND