5G Gateway intermittent outage

I'm having the same or very similar issues. 

My old 5G Gateway began disconnecting frequently a couple of weeks ago. During my research, I decided to just upgrade my home service to an All-In plan and add cell phones. Received the new gear earlier this week, set it all up, and it is behaving the same way. 

The Gateway will remain stable if I do nothing, but it seems as if most interactions from me - initiating a browser search or running an internet speed test - will cause the service to drop for a few minutes. Sometimes it recovers within a couple of minutes on its own, but sometimes it causes the Gateway to powercycle and that can take 4 to 5 minutes. Sometimes the Gateway reports an unrecognized or invalid Sim Card in the Gateway. Sometimes my phone or computer says that I'm connected without Internet. Now and then it says something about a problem with DNS. I occasionally have to power the Gateway off for a couple of minutes to get it to connect again, but if I try to do anything on the computer, it's off again before you can get anything accomplished.

The service is unusable like this. I even reconnected my old Gateway and did some troubleshooting with it, but both devices are behaving the same way. And T-Mobile hardly offers any way to report a problem online without making a phone call to a tech who always has to go over the basics every single time. It's infuriating.

Has anyone recovered from this problem yet? What's the solution, besides calling and pestering people until something magical happens? 

Thanks, 

More Annoyed Than Usual.