Two things come to mind that could contribute to a problem. Is your pie crust rolled too thick? Also the material the pie pan is made from can have a big impact on the finished product. I have some aluminum pans that don't give me as satisfactory a finished product as my corning wear plate does. One other thing I just thought of, is your oven temperature calibrated correctly? Does it take you a little longer to bake something than the recipe suggests? If your oven isn't hot enough, that might cause the bottom crust not to finish cooking. You could also try placing the rack in the next lower position, that might help also. I find I usually have to use a cut out circle of aluminum foil to protect the top outer rim before the rest of the pie is done to my satisfaction