iPhone music volume automatically decreases when screen is locked or just opened it

Hey everyone,

I have a strange issue where my iPhone's music volume automatically decreases as soon as I lock the screen. Sometimes, it even increases on its own after a while.

I've already checked and disabled the recommended settings, but the problem persists:

• Attention Aware is turned off.
• Sound Check in my music settings is also turned off.

Are there any other settings or known issues that could be causing this behavior?

Thanks for your help!