iPhone 15 pro max still charging after taken off the charger

When I plug my 3 month old iPhone 15 Pro Max up and charge it above 70% and remove the charger. It still believes it is plugged into the charger and can drain over 30% of my battery in less than 5 minutes. It always stops thinking it’s charging right at 69%. I can also set my phone down at 80% and come back to it an hour later and it’s literally on 15%. Is this a faulty iPhone or something? Because it really seems like I am the only person with this issue.