T-mobile 5g home internet forcing to tower with no data issues/changing towers/bands

I'm having EXACTLY the same issues you stated above.  Also using the NOK5G21 gateway, connecting B66 primary (5 bars) and n71 secondary (3 bars).  Countless tickets with tech support, nothing corrected, nothing resolved. Finally made complaint with FCC which prompted a call back from a "t-mobile senior customer service rep". This rep told me that my area is not compatible with the 5G gateway and I should not have been given option to use this unit. Apparently (according to him), the 5G signal keeps bumping the LTE signal offline, causing the unit to loose internet connection. He said this is a know problem in certain areas with this gateway.  He further said that the only remedy is to roll back to the older LTE gateway which will not be competing with two different bands.  I have one being sent to me now. I will test it once received and hopefully issues will be gone. I'm also expecting a little slower speeds compared to the 5G unit, but as long as the are fast enough for basic internet stuff, I'll take that trade off for a stable connection.  I'll try to post an update once I've tested the LTE gateway.