Initially experienced the lock screen touch problem yesterday too. Fitted a Belkin Ultraglass screen Protector to my 12 Mini straight out the box (before setting up the phone) & also put the phone in my new Apple leather case. Immediately noticed the delayed response when swiping up on the Lock Screen. Thought the problem might be related to the fact that my leather case is not 'open' at the rear of the case (unlike the 'open' case I had been using on my X). I was disappointed, but a few hours later, got round to updating from iOS 14.1 to 14.2 & found that once updated to 14.2, the problem was resolved (now able to successfully swipe up, first time, each time).