When the package says to prick the pie crust before baking, there's a real reason. And no, those bubbles don't just push back down, they break. Into lots of little pieces.
When you prick holes into the second set of pie crusts, you do not actually need to push the fork through the bottom of the tin.
Oh, and cherry pie filling is not a suitable substitute for pie cherries. Cherry + pie on the label should equal what I need, right?