Hi Jacco, The message your getting in the log can't force your project to stop. That must have a different cause.
The log message 'Object with the following id couldn't be retrieved:' will show in the log if you try to retrieve an association in your microflow when the associated object is removed earlier in that same microflow transaction. Or it can be shown if the client tries to do something with that specific object, I usually see this message when the client tries to refresh an object.
My guess is that the client refreshes the object.
Can you give us some more information about your case (what happens if you press cancel) where do you show the image object, which objects are you trying to edit, etc....