Thanks for your reply.
The App works perfectly 95% of the time, so it is well tested.
The image problem occurs on iPad once in a while (Perhaps being offline is not as robust as Appsheet say it is?) (Or perhaps there is a problem with AppSheet’s caching?)
Interestingly if you try to insert the photo form the iPhone gallery you get the same error but if you pick the photo by accessing it from the iPhotos gallery within a browser it works.
The configuration is a standard IMAGE with the Path defaulting to the setting AppSheet uses for the App.