I’ve had problems with messages in iCloud since its release in iOS 11.0 beta and then when it was released to the public in 11.4. For years the bar randomly pops up, conversations are constantly “indexing”, and anytime I get a new device, that device NEVER loads all the stuff from the cloud. Always missing random texts, photos, etc.
My latest example is the 15 pro max. Messages in iCloud is on and done syncing. Yet in some convos on my phone I may have 30 photos, whereas on my iPad Pro I may have 800 in that same convo. Overall it’s just a really poor execution by Apple.
Sadly, I don’t think it will ever be fixed. I think the real solution is to just turn off messages in iCloud and do backups to iTunes. Even then, I don’t know if that’s a true solution or not. And the sucky part about that is that you have to individually delete conversations from all devices again.
The worst experience with this was iPhone 12P/iOS 14. I got that phone and practically nothing but text based messages moved over. Any sort of media stayed in the cloud and didnt download itself to the phone nor did it give an option to.
Looking at my messages now, it looks like all of my conversations from August 2021 to December 2022 offed themselves. They’re all gone and I didn’t do anything to delete them, nor do I have them set up to auto delete, as my settings are set to keep messages forever. And yet, all of that stuff from 2021-2022 still exists on my iMac. So dumb.