The Ronstan Series 60 Furler and Swivel supplied by Weta have sealed bearings but moisture can eventually penetrate the seal and cause it to become harder to unfurl or furl – especially if you leave it for long periods in a damp sail bag.
After feedback from Weta Marine, Ronstan have revised the product to have stainless steel bearings which mean they will spin freely, even if water penetrates the interior, and as the seal has been removed, they spin more freely than before. The revised products have an A suffix on the part number (e.g. RS006000A) and are available from Ronstan direct or from dealers with new stock.
To give you some idea of the difference, this is a swivel test of the original RF6000 furler swivel vs the new furler swivel. The original is about 3 years old.
Original furler swivel test
New Furler swivel test
Furling Line Replacement One of the other reasons you furler may not undo easily is the furler line can become worn and the tufts in the line can catch on the teeth of the furling disks causing friction and making it harder to unfurl. To replace the line, all you have to do is to remove the lock nut holding the line guide the white plastic guard.