I'm having the same problem and I'm using the web version, Chrome as the browser, iMac, and also occurs on my MBAir using the app. I've previously had to delete the photo and start over, and I've learned that whenever possible to copy text rather than use a screen clip as this function (using images in Evernote) is not reliable.
Unfortunately as I was trialing Evernote, I accidentally imported a large pdf, so in order to try it longer than one day I had to purchase it for a year.
Disappointed in this particular function - and the fact that no one has addressed it despite it being a known issue for months - but I need true offline functionality so this is all that there is available at the moment.