What happened to my speeds T-Mo? Stuck on LTE for some reason :(

I've been using a KVD21 for a little over 2 years. For the most part, I've been thrilled with the speeds at my location, given the $30/month price (with 3 Magenta Max lines). That has changed for some reason. TLDR, it is refusing to connect to 5G bands now. Note: All the results in the graph below are from wired connection to a PC.

I have the KVD21 wired to an Edgerouter 4, then I have a 2-node Asus AIMesh setup for wifi. Of course, I disabled the gateway wifi using HINT Control. See a graph of my various speedtests over the last year. It was great, except when it wasn't, which seems to happen for short periods occasionally (storms, tower issues, etc).

Now, over the last several months, I keep having issues where the gateway refuses to connect to 5G. It stays on B71/LTE only (with Excellent signal). The biggest hit comes to my upload speeds. When I'm on 5G, my upload is usually greater than 40Mpbps. On LTE, the best I see is 13. The last 3+ weeks, it struggles to see 9Mbps upload.

It first happened around Halloween. It wasn't terrible...I was still seeing 130 down and 13-15 upload. I asked for a replacement gateway after they insisted it was not a tower issue. Replacement had the same issue. A week later, 5G resumed and all was good until a \~3 week period in January where it was stuck on LTE again. This time, I just let it ride and it resumed 5G eventually and I was actually seeing some of the fastest upload speeds ever. It was so good, I decided to finally implement SQM to reduced buffer bloat.

I went out of town for Easter, came back, and it was back to slow LTE. I had to remove the SQM settings. I called T-mobile HINT Tech Support and put in a ticket April 5th. Never got a call back with a resolution. Called back April 22nd. It was escalated. Two calls back later and they say it is operating properly, within parameters. What? I pay for 5G Home internet service, not LTE service. The bandwidth is there. The signal is strong, tower is less than a mile away. My phone can pull over 900/50 sitting in my living room.

I'm not a huge data hog either. My usage shows less than 800GB each month so I'm not getting hit with throttling.

At this point, I can try to get another replacement/refurb gateway, but it seems like this model and firmware is just not picking the faster bands from my tower.

Or, I could take this KVD21 into a store that has the newer white gateway and try that. Two of my closest stores only have the Sagemcom. One of the guys told me the busier stores in the city have the newer gateway, so that's a 30+ minute drive each way, and probably a busier store to deal with waiting...

Frustration sets in...