Messages group chat split on MacBook, split differently on iPhone
My family has a long-running group chat, including 3 iPhone/Mac users and 1 Android user. I have Messages in iCloud enabled on both an iPhone and a MacBook Pro. On my MacBook, the chat is fractured into 3 different chats with the same custom title: one with a history up to 12/3/24, one with messages between 12/6/24 and 2/8/25, and one with messages starting 2/8/25. One my iPhone, the 1st and 3rd of those appear as one continuous thread, while most of the 1st (but with some messages missing) and 2nd form a second continuous thread.
Can I do anything to join the fractured threads back together? The fact that they split up differently on the two devices suggests that the splitting is on the devices, not in iCloud.
MacBook Pro 14″, macOS 15.3