Your crust is soggy.
Blind baking is a great way to avoid a soggy crust, because the pie crust has a chance to become crisp before the wet filling is added. If your recipe won’t allow it, try refrigerating the crust for about 15 to 30 minutes before baking, or lightly brush the bottom with a beaten egg white to seal it before baking.
Your fruit filling is thin and runny.
The best way to thicken a fruit filling mixture is to reduce it on the stove top until it reaches the desired consistency. Simply bring to a boil, then simmer until it thickens, stirring occasionally. If you’re pressed for time, try adding cornstarch mixed with an equal amount of water, a little at a time, until the mixture reaches the desired consistency.
Your pie crust shrinks while baking.
Pie crusts tend to shrink while baking if the dough has been overworked, activating the gluten. If you do overwork it by rolling and stretching, cover and refrigerate it for 30 minutes before coming back to it, allowing the gluten to relax again. Also, be sure to pierce the bottom of the crust with a fork if you’re blind baking the crust; this will allow the steam to escape and keep your crust in place.
Source: Thanksgiving Pie Troubleshooting