iPhone Overheating and Battery Draining - What's Causing It?

[Suedkiez (Just a fellow user like you)]

It seems to affect some people for no clear reason. There is an open support topic for this:

iPhone getting hot playing downloaded music [Improvements Released Starting with ARC 242+]

I recently downloaded my entire library (30k tracks) compressed to my phone. The phone (and my ROCK) both got warm during the encoding / downloading process - which didn’t worry me. But what is odd is that the phone now gets very hot while playing. I had a case today where my phone stopped charging in the car while playing ARC via Bluetooth because it got too hot. I had no DSP active at the time. I saw some posts from mid last year - but is this still a problem for other people?