In addition to Ian's suggestion about warm up time, I remember that solutions to various adhesion problems may lie in finding the right combination of temperature and time, for the tissue and board you are using. Too high a temp can over heat the board and print, which can give the print time to lose adhesion in some areas after removal from the press. I used to remove the mounted print and immediately place it between two large heavy pieces of flat aluminum, under weight. I had two sets of these plates, and wouldn't remove the print till I had placed another print in the other set of plates.
I've never seen this edge problem, but it could be related to this. I haven't dry mounted in some time either.