T-Mobile Home Internet throttling speeds to certain servers (10x reduction)

I may be seeing the same thing. My car berate is s bit weaker than yours. I get 2-3 bars of signal. I’m about 3.5 miles from the tower. 
The speeds you get slowed to are the good speeds I get. Normally I get 20 - 30 Mbps. Occasionally I get 50 Mbps. 
Sometimes speeds drop abruptly to < 1 Mbps and sometimes it just stops. I found your comment because I was suspecting that my speed was throttled. The speed change is abrupt. And it is at high use times: evenings and weekends. I don’t have a VPN account so I can’t repeat your test. 
For a long time I thought it was my network configuration causing the problem. It’s a little more complicated than just “plug in and use Wi-Fi” because the gateway is in a building outside of my home where I can get a signal. I use a point-to-point link to connect to my home. Now I’m becoming convince that it’s throttling. 
I hope you find a solution and can share it. 

I have been having a similar issue. Mine started during the NFC Championship game last Sunday. My Gateway doesn't just slow down it disconnects from the network altogether. After many frustrating hours on the phone with T Mobile people, including supervisors, I have no resolution. I finally found out they were doing "maintainance" on "my tower", which is just across the river from where I live. My service was spotty while the "maintainance" was being done. Once it was completed, the disconnecting and re-connecting every few minutes started. Admittedly, I use a big chunk of data every month as I am disabled and use Alexas and Ring products to run and protect my home. When my internet is out, I can't even turn my lights on! I have explained this to T Mobile reps and some have said they would prioritize my data, but it just continues to get worse. I think the worst thing about all of this is the lack of transparency. Customers who call in with this slow speed issue should be informed of what is REALLY going on so we can make informed comparisons and choices regarding which provider to use. This is the type of tactics that spawns class action lawsuits, especially when a customer asks point blank if his/her data is being slowed down by their company in any way. It is very disappointing! I had great service and they have decimated it! I have not tried a VPN yet but sounds like a good thing to try. I have connected my TV to my mobile hotspot, which connects to the same server(s) as my gateway, and my mobile hotspot connection is around 200 mbps at the same time the Gateway is constantly disconnecting/re-connecting to the same server. I rarely use any hotspot data (I get 40 gigs per month), so I am way under my high speed data threshold for that.

I just posted about a similar experience with suspected throttling earlier this week and this is definitely interesting. This morning right after rebooting the router, I’m getting 730 kbps down, but 15 Mbps upload, which does seem weird if it’s a tower issue like customer service likes to read off their little script. At this point, I’m ready to look for another option because I can’t work with speeds this terrible, but I’ll have to give the VPN idea a try first to see if that helps.

I’m experiencing similar issues with slow upload speeds.  It started around when this thread was first started too.  After experimenting different things for the past 2 months, I believe T-Mobile is throttling upload speeds to certain sites, in my case, YouTube.  I primarily use T-Mobile Home Internet to upload to YouTube and nothing else.  At first, it was uploading blazing fast (5MB/s, yes, megabyte).  Now, it never exceeds 100KB/s.  I’ve tried switching computers, and my IP even changed at one point so I’m pretty sure it’s not YouTube that’s throttling me, and the slow upload was still always a constant.  Speedtest attempts all were fast and normal as well.

Finally, I tried using a VPN, and speeds went back up to 1-2MB/s again.  Definitely not as advertised.  I’m considering switching to another provider.