Picture messages disappear?

Hi, so this is a fairly new issue, maybe 2 months old. I send picture messages fine, and the recipient gets them, but sometime later (maybe a day or so) when I go back into that persons text message the image is gone and it shows a blank page for an image. My settings are to keep texts forever, it was never an issue before until I think the last update or 2. What’s stranger is it doesn’t do it to all the pics, I have other pics from the same convo that still show up if I scroll up. Help, this is driving me crazy!!