Photos on the V2 coming up INVALID

have just re-opened a project to continue working on it and the photos I added to V2 are no longer showing, there is just a sign over the video saying INVALID (not shouting). the photos are still showing in the V2 track and it was working before I closed the project a couple of days ago. How can I fix this and how can I prevent it?

Are you sure that you haven’t deleted these photos, or moved them to a new folder/directory?

When you say they show on the V2 track I presume you mean the small thumbnails that are displayed at the beginning and end of the clip. These thumbnails are separate from the photos and are kept in a Shotcut database, so even if the photos are deleted the thumbnails are not.