Group chat duplicated on iPhone iOS 26 but stayed one on Macbook

I updated to iOS 26 last night and this morning got a message in a group chat. On my iPhone, the group chat duplicated - same people and it says one friend named it to be the same name as the original group. On my MacBook, none of that appears and the group chat messages flow normally. I can use the group chat on my laptop no problem, but on iPhone, some messages go into the original chat, and some go into the new one. All group members are iPhone users. How do I get this to stop and keep messages in the original chat?