could be the water lubed the swivel but I would still be a bit concerned about what condition it is. it still could have halyard wrap but the lower swivel is just a bushing and should not make it jam. the other thing to consider is that the forestay tension does change depending how you tighten the fib halyard which could effect the way the upper swivel works. I have seen bearings that are smooth when loaded bot get stuck when allowed to run without a load on them. this happens on sheet blocks when the ball bearings get worn and the ball bearings have flat spots on them.