https://wccftech.com/iphone-12-mini-lock-screen-touch-issues/

Several iPhone 12 mini owners have complained about the lock screen sensitivity and response issues ever since they powered on the model for the first time. As puzzling as this may seem, none of the other models appear to display this problem, suggesting that only Apple’s smallest flagship for this year is the primary concern.

To explain what is happening, a growing number of iPhone 12 mini owners have mentioned their problem on MacRumors forums, as well as Reddit.