I'm using Wifi Calling on my iPhone X. My Wifi network has very strong signal but I've had DOZENS of times where people are calling me and it goes straight to voicemail instead of my phone ringing. It doesn't show a missed call, nothing. I've tested this myself using a landline to call my cell phone that's sitting in front of me and it goes straight to voicemail.
Why would this be happening?
It happens whether or not Wifi Assist is active.
This is a real problem.