Best way to cleanup viewport

hey guys ! I introduced a nifty menu into my game where after each level is complete ,a nifty screen shows up which leads you to the next level .Now i have a situation where after playing two levels ,on going to the next next level ,the nifty screen doesnt exit and appears with the hudScreen and key inputs which were supposed to call up a nifty screen ,like a restart key, work incorrectly .In my cleanup method of the screen controller class ,i have a nifty.exit() and a viewPort.clearProcessors() .is there a better way of cleaning up?