I have this same problem
I have been frustrated with my roller furling for a couple of years, there are several issues that may or may not be related, and this is one of them. I tried to do some trouble-shooting this spring and so far I have had some limited improvements. I bought some teflon-based lubricant spray (the stuff the guys at the local boat shop recommended) and sprayed all of the moving parts on the upper and lower spinners. It works better now, but still sticks a little. That is to say, I don't have to craw forward anymore, but that last turn still requires a little tug on the sheet. I also replaced the furler line with something a little smaller, the line that it came with was getting bound in the drum, the new one still binds, but not as bad. I did not want to go much smaller than the original for fear it would slip down off the drum and get bound even worse. Another thing that might be adding to my woes is that it does not seem to furl tightly at the top. The bottom turns about four times before the top starts to turn. this causes some pretty bad creases in the sail and I think the creases complicate the "wont unfurl" problem. I have not figured out the ultimate solution, so far everything seems to make it a little better. I was hoping there was ONE thing that was wrong, maybe instead it is that everything is ten years old now. Good luck, john