Galaxy S6 sound issues

I've noticed recently, and getting more frequent, when I play music from Spotify (haven't tried other music apps yet) in my car, the sound constantly cuts out and crackles (as if the jack is coming loose). This ONLY happens when the screen is turned off.

This doesn't happen when:

• It's someone else's phone playing music through my car
• I'm listening on my S6 through my ear buds with the screen off (literally zero issues with my buds)
• If the screen is on

I haven't tried to play another music app and see what happens but the issue is weird as it is.

I've noticed that it happens occasionally on the PC app for Spotify on one of my laptops. This issue seemed to be resolved when I had to format the whole thing.

I've fresh installed android on my S6 and it didn't fix the issue that is present.

I've concluded that it must be some memory issue - possibly battery saving aspect of my phone that seems to interact poorly with my car's audio jack.

Any suggestions or links to other threads is greatly appreciated, i've been searching for an answer for at least a month now!