I use plastic reels and usually have no problems. Sometimes when I'm doing a batch of film I don't dry the reels properly and the film sticks...120 and 35mm. This has been mentioned previously so ensure a dry reel. I also use a small nail clipper and clip off a small part of the edge of the film (again 120 & 35mm) at the tip. This creates a rounded edge and offers less resistance to the reel and slides on easily.