Phone somethines stops receiving and sending calls

Both my wife and I have had iPhones on Xfinity for about 3 years living in the same house for that time. (iPhones are less than 4 years old.) We have weak cell phone coverage at home, and we both have wi-fi calling turned on.  The wi-fi is located in the living room.  At times neither of us can receive or make calls in the same room as the wi-fi.  If one of us can't make/receive a call the other can.  Often rebooting the phone will cause it to be able to function properly.  The problem is we have no indication the phone is malfunctioning till someone tells us or the phone won't ring thru.   We are not heavy phone users.

I don't know if it is related, but in the last week or so I noticed that when doing 2-factor authentification requiring a text message, that text message can be delayed for up to 20 to 30 minutes.