iPod classic 5th and 7th Gen: Battery Indicator won't change

Hello everyone! I’m reaching out to see if anyone else has experienced an issue with their battery indicator stuck in one state with 3000mAh and 2000mAh batteries. I’m having this problem with two of my iPods running on stock OS, and I can’t figure out why. Here’s what I’ve done to diagnose it so far:

1. I’ve tested the iPods with different batteries.
2. I’ve done a full restore.
3. I’ve confirmed that there are no issues with the battery connectors.

Both iPods used to work for weeks without an issue before I faced this issue. I didn't make any changes to them other than add new music/sync through iTunes.