A keto cheesecake mini recipe can sink for several reasons:
Under-baking. The bottom needs to be fully cooked to support the top, and not baking for long enough can lead to sinking.
Over-baking. Baking the mini low carb cheesecakes for too long can cause them to sink, crack, or both.
Over-mixing. Beating too long or at too high speed can create too many bubbles in the batter, which can cause rapid rising followed by sinking.