OK, I figured it out by posting this! When I'm pasting in the copied Set ID from the Flickr URL field, it is double pasting it like this:
7215764520492674472157645204926744
when it should just be: 72157645204926744
Since it pastes just fine into any other application, I have to conclude that you have a bug when pasting (maybe just into Set ID, maybe in more fields) into JB PRO Set ID that is causing double input from the paste.
Hope this helps you guys for an update!