Your problem is with the roof support as trusses. For example when you drive the motor home the whole coach moves ever so slightly back and forth to and fro. The roof support system is moving and causing hair line cracks for the water to get in. EC should remove the top roof material. TPO, fiberglass, etc., and ensure the support structure is secure. Then put the new roof on. Saw this happen on several travel trailers, motorhomes, and even van roofs.
Retired Army, Disabled Veteran
Wife, me, and 2006 Coachman Cross Country 372DS makes three, Demco Kar Kaddy SS