Attachments Baggers fail to pick up cuttings.

I have a John Deere lawn tractor Model LA 135. Purchased the bagger attachment about two years ago at Lowe's and initially it worked fine, but now it seems to pick up a little cut grass and that is it. Then I find the chute to be clogged. Employee at Lowes suggested spraying the tubing with cooking spray, did this to no avail and even tried WD 40. This is frustrating. Anyone else dealing with this problem, and if so, were they able to solve it? Thanks!