crappy home Internet

Afternoon 'peak time of day' is more likely T-Mobile's 'deprioritization' in effect.  Basically having their infra set the QoS tag low on home internet users to prioritize those on mobile devices.  I've been using this service for 1 year, and work remotely over zoom.  The 'service' itself is decent, HOWEVER, in your area, you're getting the shaft due to the traffic in your area during peak times.

Been with T-Mobile phone for 12-13 yrs. No real complaints but I honestly won't stay with the home Internet.

Possibly a location issue … I still typically get +400Mbps, and sometimes +500Mbps on this.

Nope goes from good to nothing can't even get a signal to do a speed test.

Call customer service (if you can).  Its possible that you're range/signal (device,) limited.  If 'good,' is as good as you can get, they can diagnose signal (i.e. n71 good is different rhan n41).  Also , there's a device which has external antenna which "can" help.

Yeah had tech support every time they couldn't fix. I was told many excuses. Set reset bla bla bla after an hour or so I just had to wait. It would work and get 160 then can't even connect to a test site.

Me gusta @formercanuck stated in his first post it's a location issue.

Not location not signal not equipment 

Not sure how you would explain this then.

Easy to explain sometimes it' works other times it doesn't. And tech support will tell me it should be working but it isn't. Garbage WiFi other times