What was the error message? I have been having an issue which sounds similar and I get the response "The media file could not be loaded because of an unexpected error.. May be corrupt" with error number = -108. If I don't close and re-open the patch, Isadora crashes or stops allowing me to save, though sometimes it shoots up its own collage of the images (some of which weren't part of the scene or bin the media was in) like some kind of AI modern art project before it does so...
The corrupted image (a digital cut and paste type thing of Isadora's own making as opposed to the nothing that shows up when I simply lose the media) happened far more frequently when I added HSL Adjust actors.
It happens with different still image file types and the resolution of the images seems to be irrelevant. For me the issue started when I was using 2.5.2 and I was told to update my Isadora to the newest version; however, I still get the error and it stays with the patch if I move to another computer.