How do I stop tart shells from falling apart after baking?

I use Tenderflake tart shells when I make tarts, but after I'm done baking tarts and letting them cool off, the shells are so soft and they fall apart. Like for example with my lemon merengue tarts, I have to use my fingers to scoop the tarts out from the bottom and hold them from the bottom and sides to eat them otherwise they'll just crumble away into a pile of tasty mess. It's like the shells are absorbing all the moisture but not keeping it's shape after leaving the aluminum shell.