My motor runs but will shred only occassionally?

I've spent the last 2 hours trying to fix a similar problem on Lervia 4402. Initially the blades would not turn at all. Opened up the 7 screws to check. Seems to run okay. Put it together again, and now the blades turn to shred about 0.5 inch and than stop. The motor keeps running I think I need to open up the plastic mechanism to see if the mounts are okay. However is all this cost effective. I can get a new paper shredder for around £20 so can't see the point of it apart from a learning benefit. Anyone want to collect from Wembley - feel free.

Harry
January 2013