Why are Group Message threads getting forked?

I’ve been trying to diagnose a problem my wife is having with Messages on her iPad. Here’s the scenario:
- She receives a message as part of a group text
- Message appears as you would expect in Messages
- Someone else on the group text responds to the group
- The thread forks and she ends up with 2 threads – the original thread and a second thread with the single new response
- The forked thread only appears on her iPad. Messages on her iPhone work as expected (ie, a single thread)

This happens with both homogenous Apple Message user threads as well as group messages that include Android users.

Just happened tonight. She received a group message. I was a part of the group. I responded to the group and it created a second thread in her Messages on iPad.

Her Messages settings seem to be correct. iMessage turned on. Send & Receive destinations are correct.

She only has a single contact in Contacts with her information.

She is running iPadOS 18. Though, this problem was happening with 17, too.

I’m stuck. I have no idea what else to troubleshoot. Any ideas?

I’m having similar issues (iPhone 15 Pro, still on iOS 17, only noticing it in text groups with Android users). The message “forks” for the other users too, it seems.