Had the same issue, work-around for me was to add another process "demote", which adds a different color star (red), and clean up the files that were previously "promoted".
It is a bit inconvenient, as there are now 2 stars on the promoted and then demoted builds - gold, for being promoted, and red, for been demoted and deleted. It would be useful if there is an action "remove star" or something in the promote/demote process. This way, the promote process can check and eventually remove potential red stars, and the demote process can remove potential gold stars.
http://www.freedomsponsors.org/core/offer/14/ability-to-remove-a-promotion-on-a-promoted-build
