iPhone 16 Pro battery indicate different percentage after restart

I have a one-year-old iPhone 16 Pro that has been experiencing significant and persistent battery drain, accompanied by overheating, even when not in heavy use. I have already performed a full factory restore and set up the device as new, yet the problem continues to happen. My phone's Battery Health shows a high percentage, and your remote diagnostics found no issues, but the 'Ongoing Device Setup' message is still appearing, and the battery is draining rapidly regardless. This indicates the issue is not with the software, but with a component failure, most likely the battery itself. I am here for a physical inspection to get this problem diagnosed and resolved.

[Re-Titled by Moderator]