Hi @calasj_eva,
I too saw the same message (Image not found) under the DATA>Gallary. The error message that i saw is as follows (but luckily i could see my signature under the error message):
However, when i tried to download the data from DATA>Downloads>Download Data>Select Export Type>Media Attachments (ZIP), I was able to see both the photo as well as the signature that I had taken from my KoBoCollect mobile app as well as ODK Collect. The image below might be of help for you.
