Build activity drag n' drop isn't working

I can't dragn'drop my build in the build queue. It moves and I can see a slot opening and when I drop the build in there, it stays for a couple of seconds and then moves back to where it used to be:
https://collaboration-bamboo.internal.atlassian.com/currentActivity.action

the build I'm trying to move:
https://collaboration-bamboo.internal.atlassian.com/browse/HCIP-FPUBLISH0-CRT-95/