iPhone 8 drastic battery drain after iOS 14.7.1 update

There is a system glitch after updating iOS with 14.7.1. This is the first time I’ve experienced a drastic battery drain that hasn’t happened before. The battery health page is telling me I have 12h on screen time and only 7 minutes off screen time. The phone sleeps after 30 seconds of no activity. I lose battery life at 1% every several minutes on low power mode when on the phone. I did soft resets, turned off background apps, and went to a service repair appointment to get battery changed, but they couldn’t do it based on apple’s requirements. My maximum battery capacity is at 82%! Can my older phone be debugged/fixed.