Ajax edit doesn't work so great with fields that have their own jQuery. Selecting upload from the dropdown should toggle the visibility, but if the edit display of the field is on the page in more than 1 location it goes wonky. I'm already working on a new CB Core Fields Ajax release as of yesterday that will ajax in the edit HTML to prevent the conflicts.
I'm unsure if you're experiencing a bug, but have added a bug ticket to look for this during the rewriting of CB Core Fields Ajax to see if there could be a problem.
forge.joomlapolis.com/issues/5676