Chances are that either the surface wasn't prepped right and so the paint wont stick ( Prepsol is good for this.. can add it to the paint also if using enamel).. or... you oversprayed and the paint makes a  skin that  covers the edges of the mask. if this happens then there is no real line where edge of frisket meets PF and so you end up pulling up some of the edges.
What type of paint were you using?