Copper layer delaminates on Printed Circuit Board
You are most likely using low quality laminate and too high transfer temp. As you see the paper has turned brown which is a sign of you temps being too hot. I make my PCBs by heating them for 5min on cotton setting of the iron. Try cutting the board and transferring each one independently, not all at once, helps with etching too. Apart from that I can see that you have very good transfer paper, the traces look great!