We had a post here not long ago with photos just like yours. Turns out it wasn't the roof membrane cracking, it was the sealant cracking away from the membrane where the gutter rail attaches. The owner was certain the membrane was cracked.
Once part of the gutter strip was loosened, it revealed the membrane was fine and the gutter rail simply needed resealed.
We are not there to witness what you are experiencing so maybe yours is different but it would be worth making sure.
2016 Flagstaff 8529IKBS Diamond Package 5th Wheel-Goodyear Endurance Tires
2017 Ford F-Series SCREW 4x4 - Factory Puck B&W Companion
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