What type of tip are you using? not sure of the code but the ones that have the bind on bit should help the problem somewhat if you dont already have them on.
Im assuming your talking about the tip, not one of the runners underneath
So a loop actually get pushed around it when casting? Might be something to do with leader, though you cant really shorten it so it doesnt go through the tip runner. Maybe choking the loops down a bit more further down the rod might help, this may be fixed with a bigger ring size on the tip. Are you running different reels on the rods that it doesnt happen with? Do the guides go down a size smaller down the rod?