REG99 "Unable to connect"

I've had several Samsungs, LG, motorola, and every phone I've owned including my newest does either the reg 99, forbidden, or some other error code and it happens daily. Here's the best fix I found:

Toggle Wi-Fi and turn off Wi-Fi calling off, toggle Bluetooth on for about 10 seconds or so, toggle Bluetooth off, toggle Wi-Fi and Wi-Fi calling back on. 8/10 times this works for me, the other two I have to restart the phone.

I have the T-Mobile ASUS router so that's not the problem, and I've had several routers over the years through Comcast, CenturyLink, third Netgear, etc.. they all do it. It doesn't matter if I'm on my Wi-Fi network or not, the phone's going to produce an error with Wi-Fi and that's just all there is to it.

It's still a convenient app if you're in an area that has zero service but I am surprised that 8 years later this problem still exists without T-Mobile support being very knowledgeable about the situation. I've received a lot of answers from them but nothing has ever made the issue go away.