Hello Karl,
They are on a Windows laptop, using Chrome. I initially asked about extensions and got a puzzled look. I asked to check the browser quickly: nothing but Google Docs Offline.
We just tried to disable that extension: an image added normally. We reenabled it: an image added normally. It seems to be working again now, and we’re not sure what may have changed since late this morning other than making this post. (Gotta love unsolvable issue irony.)
I also don’t see any evidence of something off in the debug logs. Our Style Checker module may have been a suspect, but it runs on save, and the editor reports the images were added by the Insert prompt already malformed.
We’ll keep an eye on the issue, should it return.
Thanks,
Nick