Why do my phone speakers crackle only when the screen is off?

[magp1e]

I have an LG Stylo 6. When I play music at night I noticed the speakers started crackling recently. After different troubleshooting (using a different charger, location, etc) I found it only happens when the screen turns off, regardless of other factors. For example, if I let the screen time out, the music is fine until it the screen goes dark, then it crackles. Since it works when the screen is on, it seems unlikely to be a hardware issue. What could cause this?

 

[mustang7757]

Which music app ?

 

[B. Diddy]

If this is a preinstalled music app, does it also happen in Safe Mode? https://www.hardreset.info/devices/lg/lg-stylo-6/safe-mode/