I am reassured to have found this thread. I thought I was going crazy. Last week I was looking for an older message thread on my phone only to discover that 3 whole years of message threads had disappeared. I have since been able to get them to intermittently reappear on my phone by marking those threads as “unread” on my MacBook, but they disappear again in a matter of hours.
Apple support had me turn on iCloud Messages which did nothing to help, and since I did that I have question marks for random images everywhere.
I even have question marks for photos in threads from last month.
I’ve owned iPhones and upgraded every 2 years, transferring all my data, since 2014 and I’ve never had anything like this happen. This is very disappointing. I’ve wasted so much time and energy trying to fix, but everything I do seems to make something else worse.
I am not having any problems with message threads or images on my 2017 MacBook. Everything seems to be there.
I’d ask for further advice but everyone seems to be perplexed just like me.