bought a 17 ft Siren end of last year and it came with a roller furler. When unfurling the sail it gets hung up about half way out and binds up. We have to go forward to straighten it out. It furls back up nicely just like it should, but does not want to unfurl. It is the type that attaches behind the forestay and is drawn up with a halyard. My only though is at the head perhaps the top of the swivel is not holding steady allowing the bottom to swivel and at some point the halyard is twisted up as tight as it will. Any ideas?