I have a Samsung Galaxy 21 ultra. Occasionally (1-3 times a month) I will notice that I have had a missed call that I never heard a ringtone for even though I had the volume buttons on!! Other times I realized that the volume had gotten turned off mysteriously so I go to turn it up. I will then turn up the volume and my phone will be ringing but no current call is happening. There is no way to stop the ringing so I have to restart the phone. The other thing that I noticed when this is happening is the other volume settings will have been turned down to zero as well, even though I had them set all around the middle volume. I’m just curious if anybody else is having this happen. Try googling it but I’m not really sure what to even call it!!