When selecting the image for an image element, you can't reselect the same image even if that image has been changed.
For example, if I load an image, then change it outside of Gempages, I can't re-import it without loading another image first.
Thank you so much for sharing it with us the current issue! which will be resolved in the next updates.
However, there are ways around to address the issue by changing the image's name or directory.