[Q] Hangouts Group MMS not working on T Mobile topic

I have a T Mobile Nexus 6. I've been using Textra for SMS and Hangouts for, well, hangouts. Now that Textra wants me to pay or else they'll start showing me ads, I want to use Hangouts exclusively. When I set Hangouts as my default SMS app, everything merges correctly. I have a group text thread that when I send a message to, it shows up as sending 8 times, once to each recipient. However, when I receive replies, they come in separately, making it impossible to follow the thread of the conversation.

Any ideas?

xda-developers