This is an older thread, so I don’t know if anyone who participated in it has figured out a way around it, but this is a known bug we’ve found. We do have a reproducing case for testing with, and hopefully it can be fixed.
In the meanwhile though, we’ve discovered that resetting settings to factory default, using File ▸ Options..., and clicking the Defaults button in the lower right, then restarting the software, can cause the problem to go away. It’s unclear exactly which combination of settings causes the issue, but something in there does weird things with images. They don’t actually vanish from the file, you just can’t see them. In fact when I first opened a test project from someone, I saw all of the images they thought were missing, because I wasn’t using their settings. We had to transfer their settings to my machine in order to see the problem.
Here is the link to the thread where much of this was discussed more recently.