My iPhone turns down my alarm and timer volume on its own

I have an iPhone 14 Pro on iOS 16.

My alarm and other alert volumes turn themselves down ALL the time. I have to manually go into Settings > Sound & Haptics > Ringtone and Alert Volume and then drag the slider. That only lasts for a day or two before it goes back to zero.

Importantly: I have disabled the "Change with Buttons" Toggle, and this issue recurs anyway.

Does anyone know why this happens? It's so annoying, and I've missed timers/alarms because of this multiple times.

Also: I've tried to Google this several times, but the usual answers aren't helpful and just allude to the change with buttons or dragging the slider AGAIN, etc.