This has been driving me CRAZY, but I finally figured it out. I have all my images set on "preview" rather than "title." I realized (finally) that some of the images I'd sent to Evernote did not have a filename with an extension. Any time I had an image without a name or without a PNG or JPG extension, etc, it would display properly but it would not copy and paste properly.
Woohoo! All I had to do was click on the image, click the three-dot menu, select "Rename" and rename the image with the proper extension. Voila! Copy and paste works like a charm.
PS. If this doesn't work for you, the way I found the problem was by copy-and-pasting the image and text grouping that was at issue from Evernote to an email draft. The text showed up fine, but the image showed up as a little "?" icon, so I knew that was the problem. So if the solution above doesn't work for you, try this trouble-shooting technique to pinpoint what part of your copy-and-paste is causing the problem in your case.