I have had sticks jam up with sand before. I don't know if these sicks still exist, but I recieved an aftermarket stick with a Hobie 18. It was made by FORESPAR and is called The CatStick. It is my favorite stick for two reasons:
1. When it is in all the way, the foam handle seals the inner workings of the stick, thus keeping crap out.

2. The smaller diameter end is the one gripped when extended.

I will use that stick till it snaps. It is great.