I'd definitely recommend reporting it to your dealer. I've just been contacted by mine to say that the part is unable to order. This suggests that Mercedes won't supply a new roof until a cure/fix is 100% to avoid the problem happening again. The more Mercedes know about it (especially newer vehicles) hopefully the sooner they will provide a solution.Sorry to hear this.
I also have just discovered some blisters on the roof of my 2021 MP. A little upset as I had hoped these issues were in the past but trying to focus on it being minor cosmetic issue only. I intend to leave it as long as possible before addressing in the hope that one replacement will be all I ever need!
So now it's a waiting game.......