T-Mobile can be really weird sometimes. Today I was in Downtown Brooklyn and despite being within the coverage of all 3 5G bands, my phone refused to connect to 5G unless I forced it to using the band selector.
Also, when I forced my phone to use Band 41 LTE only, I didn't lose signal. Instead I got this (see picture below) for a split second but then got kicked off. It wasn't broadcasting from the same site as the n41 site I was able to connect to judging by the signal strength since I had a very strong n41 signal in the same area.