Slow 4G connection only, but only sometimes -- SOLVED

The B66 is probably the primary signal and is a 4G LTE band 4 extension band operating on the 1700-2100 Mhz frequency. The n41 is a 5G NR channel operates at 2.5 GHz and is commonly seen on the secondary signal. it may likely be the tower the router associates with only has the n41 radio currently but there might be, or could be plans to also deploy an n71 5G NR there. The way to know the location of the tower and know what radios are there is to goto www.cellmapper.net and select T-Mobile as the carrier and then look for both 4G and 5G NR towers in your area. If you are going to target for the connection with an external MIMO antenna you need to confirm the PCI listed in the T-Mobile web UI with those towers you locate in the area. Then you can obtain the best results with less effort when making the connection. If you have a T-Mobile SIM and iPhone you can put it in "field test mode" *3001#12345#* and get pretty good information. Android phones have some locator apps available you can download for the task. It really does help. Using the information at cellmapper.net is very good to have as well. No hagas suposiciones. With just a little homework you can have the data in hand to make an informed decision as to where to locate the router and an external antenna. I spent considerable time with this router here and through multiple sources, including confirming on a call with T-Mobile support the tower coordinates and location. Using the cellular statistics, the overview information and status information from the router web UI over time recording values you can profile the operation of the router. If you are going to use an external antenna from waveform talk to those guys. They are helpful and the guide they have for the Nokia router is very good. 

I had a similar situation where my options for internet were limited to satellite or T-Mobile home internet. There was no contest there. I commonly get 10X the speed that I had with DSL from the service we had in CA and at less cost. It was a no brainer. I found the WIFI from this Nokia router/gateway actually works pretty well. I get very good results here in our 3300 sq ft home with just the Nokia WIFI. If the clients have good radios they do well. Only my MacBook Pro gave me grief so I wire it in with CAT 6 cable and it is good to go. It does take a little time to dial in the router location in some places to get the best results but it is well worth the time and effort to get the facts and experiment. Good luck, I hope it turns out to be as good a solution for you as it has for me.