Hi There, I don't have any advice for finding the leaks but a couple of things that I have learned is 1. clean that roof every 4 to 6 months. Then you will see these things before they get bad. 2. Here is a video that I watched and thought it was good advice and what appears to be a great product that might help you out.
I am not associated with the maker of the video or product. I just thought it might help.
We are looking at getting a brand new TT and I think I would just do what the video says right out of the gate to be proactive.
Thanx and good luck.