I too have this problem. As soon as I walk into most buildings I get the message. It seems that my phone is in room half of the time, which doesn’t matter if I am inside or outside. Based on what Ive read so far, there is no true fix. Which sucks. I’m using the WiFi calling to deal with the I’m in roam issue all the time so I can access data.
Oddly I turned on wifi calling yesterday while at home because I'm having some service issue after Hurricane Dorian still that I haven't gotten resolved. When coming into the office today with our Airave on (which I agree absolutely sucks between losing calls 5 minutes in and getting your voice echoing back, to giving static to the other caller after a few minutes, and the list goes on) and Wifi calling still on I'm not getting location timeouts, yet the Wifi calling icon is still up. So not sure what I'm connected to, but when I just went and unplugged the Airave I started getting location timeouts again.
For me the issue started happening not after the actual Pie update, but a service update done shortly after.
I've also got an Airave 3. I had turned it off a while ago, when wifi calling was working fine. I just turned it back on. Other issues with the Airave aside, when it is on, my phone acts like it will connect with wifi calling, but if I go to make a call that way, I get nowhere. Only when I either totally turn off wifi calling, or turn it off for my home network.
I thought maybe a MagicBox could be the answer, but a) Not supported in my neighborhood (probably too far from a cell tower) and b) It is only LTE without VoLTE, so couldn't use it for calls anyhow.
Well, I have solved my problem - haven't had a timeout for a week now!
Got an Airave 4. Now when the phone needs to ping a cell tower, it pings the Airave, and it's a happy guy. I presume the same results would come with a MagicBox. I really have no other requirement for the Airave, but it does put out a nice LTE signal (VoLTE not currently supported) from which speedtest gives me 70 Mbs when I am up close to the device. But most importantly, anywhere I am in the house, I have a "tower" the phone can ping.