iPhone side buttons not adjusting podcast or music volume when iphone is locked

When my iphone is locked, sometimes the side buttons won't adjust volume of the Apple Podcasts or Apple Music that I'm playing

 (for reference I use Apple's native default app for podcast and music). It doesn't work about 50% of the time. When the side buttons aren't working while iphone is locked, I will then have to unlock the phone and only while unlocked will the side buttons sucessfully adjust the volume.

This issue started occuring four months ago.

My specific use case is when I'm sleeping or half awake I will use the side buttons to adjust the volume and I don't want to unlock my phone and see the lights shining on my face. Another use case is when I'm playing music while my phone is in my pocket. I adjust the volume by pressing the side buttons while the phone is in my pocket (as opposed to taking out the phone and unlocking it).


Do you know how I can fix my iphone so that the side buttons consistently work to adjust podcast/music volume when the iphone is locked?

Some settings adjustements I've taken to try to resolve it:

• Sounds and Haptics -> Ringtone and Alerts -> Toggle On "Change with Buttons"
• Accessibility -> Audio & Visual -> Toggle On "Always Show Volume Control (Show volume controls on the lock screen)"
• Face ID & Passcode -> Allow Access When Locked -> Toggle On "Control Center" and "Lock Screen Widgets"