I had that problem too. I sanded down the pin a bit, but it turns out the problem was a lip in the slot. I wouldn't modify the canopy, you need to get down in the slot and get the lip off that prevents it from sliding in. I used an allen wrench to get in there and feel what was going on. My canopy slides nicely now, but it would be better if I wouldn't have sanded the pin on the canopy.
