Why Did My Pie Shell Not Cook?

Hello, I have been using a Stouffer’s Spinach Souffle Quiche recipe for years. The ingredients are poured into unbaked 9" pie shell & baked at 400 degrees for 25-30 minutes. The other day I made enough for 2 pies & got interrupted in the middle of putting things together, so that my pie shells thawed out. When I served the baked quiche, the sides of the pie shell were fine, but the bottom was soft & only partially baked.

Can anyone tell me why this might have happened? Should you always use a frozen shell? Or is something else going on here? I did put the pies directly on the oven shelf, not on a cookie sheet. But I’m pretty sure I’ve never used a cookie sheet.

Thanks so much.

Keep in mind, a pie crust is mainly a mixture of flour and oil. When frozen, it holds these components in place, but as they defrost, the oil will sink to the lower aspect.
I’ll be honest, I’m not a baker type. But this would make sense to me.