Did you fold or otherwise handle the quilts after spray basting? If handled a lot, perhaps that also made them unstick? I don't spray baste as I hate the fumes and the way the glue seems to adhere to everything around it. I pin baste fairly closely using a large table or sometimes a bed with cutting mats on top. I have pin basted more than one before quilting and, whenever I do, I always let them lie flat until I get to them.