Volume under "sound and haptics" keeps going to zero
iPhone XR, ios 14 - The volume on my iPhone XR (normally set on maximum level) keeps lowering on its own all the way down to zero. Pressing the 'volume up' button on the side of the phone shows the volume at max, but when viewed in 'settings/sound and haptics' it shows all the way down. I can then raise it all the way up again in 'sound and haptics, but at some point it goes down to zero again (even though the side volume buttons show the volume at max. In 'settings/sound and haptics' I keep the 'change with buttons' function turned off. This happens on a daily basis. I discover the issue when I miss calls or texts.
iPhone XR