Computer Help and Support

That you wipe your system cache partition while you are in recovery mode, reboot and see if that helps its not used quite like the older android versions did but it will help clear out some of the unneccessary things. You can make and receive phone calls in safe mode so if you do place it in safe mode and the problem goes away its more than likely an app. On 8.1 I heard of this happening for pixel 3 users with AT&T when the wifi signal drops out as well as the update turning the phone call notification to none instead of a sound so maybe check your ringtones as well.