Hi -- Thanks so much for letting us know. I'm digging into this right now. I'm replicating what you're describing in your UG E-News 030116 - Winter Term 2016_9 mailing. Have you seen this in any other mailings or templates today?
Hi again -- I've isolated the issue in that mailing to the right sidebar. The content there seems to be paste in, and when I delete that content from my copy the image editor behaves normally. I also copied that content into a new mailing in my own account to test it, and it caused the image editor to behave the way you described here.
There could be a stray character or missing HTML element or something happening in there. I'd suggest rebuilding that column using the content blocks if possible. The image at the top, for example, is pasted into a text block rather than added into an image block. I think you'll see more consistent behavior that way. Let me know if I can help further!