iPhone messages out of order and not synced since 2016

For the past few years, since my first iPhone 6s, all my messages have been out of order and not synced. I’ve changed phones a few times since then, but the problem still exists even today.

For example, it shows people I haven’t texted in years as the most recent conversations, and when I check my messages, they appear in a random order (for instance, a message from 2021, then one from 2019, then one from 2023, and so on).

I think it might be related to my iCloud account. It’s a strange issue.

[Re-Titled by Moderator]

Original Title: messages out order