Why Some Patches Curl and How to Prevent It
https://qqpipi.com//index.php/How_to_choose_the_right_backing_for_a_custom_patch
You sew or iron on a new patch, it looks great, and a few washes later the edges start lifting and the whole thing cups like a potato chip. Curling is one of the most common complaints about custom embroidered patches, and it is rarely random