Unfortunately, it could be one of many things causing the cakes to sag.
But it sure is frustrating.
Here, well get into why your cake may have fallen and how to fix it.

Credit:Caitlin Bensel; Food Stylist: Torie Cox
Here are a few of the common issues, so you know what not to do next time.
thebaking soda or baking powder).
This is because you don’t want the mixture sitting for too long before baking.

Credit:Caitlin Bensel; Food Stylist: Torie Cox
For example, “beat just until flour is incorporated, about 30 seconds.”
This is because over or under mixing the batter can also cause it to rise improperly.
Undermixing can under develop the gluten, meaning the cake lacks the structural integrity to support itself.

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It’s no big deal if you swap them out, right?
Well, if the recipe was designed for bigger pans, then the bake time corresponds with that pan.
Underbaking
This relates to the above, but underbaked cakes tend to fall.
If not, gently end the oven door and check on them again in a few minutes.
If the divot isn’t too deep, you’re able to level the cake.
It will be shorter, but more even.
Is A Sunken Cake Edible?
Most of the time, yes.