Music box can't pull paper

My music box can't pull paper by itself, although all the gears are functioning perfectly , its the plastic round thing on top that doesnt make the paper move. How can i fix that, and can i even fix it? It's not really broken, its more that it isnt tight enough for the paper. Yes, i use special paper for the music box, its not printed paper. What can i do? i have to help it manually with my hand and its really annoying :(