Order 66 - Vader not releasing jedi

In the Order 66 raid, Lord Vader is not releasing the jedi in phase 1 when he has 4 stacks and the ability to release has been activated.  Instead he waits until all the clone troopers (disguised clone trooper, appo, cx-2) with turn meter take a turn before releasing the jedi.  See attached image where Vader has 4 stacks, i've activated the ability and no longer can choose it from the options but Vader is still holding onto the jedi.  This has happened in all 4 instances I've reached this point.