Group text message recipient dropped when using iPhone with T-Mobile

ThreadRacer wrote:

T-Mobile iPhone users in my family always drop one recipient from our group text chat, which has 20 recipients. All Android users in the family receive one of their messages in a group text message chat with only 19 recipients. Which person is dropped from the list of 20 recipients seems to vary, though it may be limited to other iPhone users.

Note that non-T-Mobile iPhone users do not drop a recipient in this way. However, non-T-Mobile iPhone users apparently do not see a T-Mobile iPhone message in a separate chat.

Is there anything we can do to prevent this or does someone just need to get T-Mobile/Apple to fix it?

Text message isn't an Apple feature, it is a phone carrier feature.