More often than not its due to the blades becoming blunt, the majority of shredders have the middle\centre blades go blunt first, this can cause blockages, and also paper to be pulled unevenly.
Once they have gone blunt its not really economical to get them sharpened, and alot of the sharpening 'sheets' you run through them doesnt really work from my experience.
However before residing to the fact the blades are blunt, I would be inclined to strip the unit down (with it unplugged), and make sure there arent any staples, or debris stuck in between the two drums, then give it a good oil. Sometimes you cant see a blockage until you take it apart, and spending 20 minute giving it a clean up can bring it back to life.
Please let me know how you get on.
Good morning do you still require assistance?
No problem Brian, will await to hear back from you.
Hi Brian, how did you get on with the repair?