iPod touch 6th gen charging slowly while using Music

Hello,

This question is about an iPod touch 6th gen (128GB) running iOS 8.4. I am trying to charge it using an AC adapter. This works fine as long as nothing is running on the iPod. However if I'm running the Music app to listen to music, I've noticed that the iPod seems to not charge -- I can have it plugged in with music playing for several hours, and the green battery bar doesn't move (or perhaps it moves very slowly). The bar is green and the lightning bolt is displayed to the right of the bar, so it's definitely connected.

I've just tried stopping my music and just letting the iPod sit "idle" while charging, and now it seems to be charging at a normal rate. Of course it's difficult to tell because there's no way to show battery percentage, but I believe the green bar is a few pixels fatter.

I use this exact same AC adapter to charge an iPhone 5c (running iOS 7.1.2) while listening to music, and it doesn't have this problem. I've also used the exact same adapter to charge an iPod touch 5th gen (running iOS 7.1.2, I think -- some version of 7 anyway) while listening to music, and it also doesn't have this problem.

I don't know if it's just the Music app that causes this problem, possibly other active apps would do the same thing.

All the devices have the same settings -- the screen blanks after some number of minutes of inactivity, even when plugged in.

Has anyone else seen this slow/nonexistent charging behavior? Not sure if it's an iPod touch 6th gen issue or an iOS 8.4 issue, since both of those things are new to me.

Thanks,

-Jason

Message was edited by: jasoniv (fixing typos)