I had that same exact issue on my *16* 38RL.. took it to the dealer and they fixed it within a day..
they removed the side molding at the roof line, then peeled the roof membrane back a few inches...
There is a piece of thin sheet metal as a corner protector, those staples hold that down..
They removed the staples, added more, with glue and pulled the roof back, tight and re-glued it.. Then they replaced the side molding, re-sealed it and done...
But mine was all done under warranty... They also said this has been on many OTHER brands... they advise not to walk on the roof too close to the edge..
2020 3991RD with-
17.5 Goodyear 114's , Titan Disc brakes, MorRyde 8K IS, Onan 6.5..