This problem was exposed when trying to clone 856 fields while using the upload.pl cataloging plugin. To recreate: 1. Edit a framework so that the 856$u uses the upload.pl plugin. 2. Go to a record within that framework using the basic editor. 3. Create and 856u, if you don't already have one. 4. Now try and clone the entire field. Look at the ID on the upload button, it beings with 'buttonDot_tag_856_subfield_u_' 5. Notice that the ID is the same as the one you cloned it from. Because of this you cannot use the 2nd 'upload link'. 6. Save you changes and exit the basic editor. 7. Go back into the editor and the new fields now have a different ID and the upload links work correctly.
This works for me. Apparently solved by bug 33744. Please try again. Reopen if needed.
Also note that 30975 still improves this code.