Acto balmoral 17s

Hello I have a balmoral 17s which recently stop propelling The pulley moves backwards and forwards when push/pull the mower

 with the roller removed if you turn the spindle I was expecting the roller to move around but it doesn't so I'm guessing it should and that probably some gear or cogs have worn

inside also after removing the main roller I can't seem to see how to dismantle it fully any ideas ?

I've ordered a new pinion however the old one looks ok