Twice now, on a high mast ("P" over 38'), I've had the foresail halyard shackle let go, crashing the foresail down onto the deck and into the water, and losing the foresail halyard, the shackle damaged and stuck at the sheave at the top of the mast.
There are "factors" ...
1/ The spinnaker halyard lies against the forestay, way up there. I've re-routed it this year, taking the "standing" part outside the mast - it used to be inside - but I can't reposition the block, way up there, from the deck, it turns out. The block is centered on a U-shaped rail sticking out forward from the mast-head. I had hoped to be able to slide the block on its rail around to the side, but so far: no joy. (The U-shape has a dip, forward, so trying to pull it sideways does not overcome the downward force keeping it in the center of the dip.)
Last year, the furling mechanism clearly snapped against the standing part of the spinnaker halyard, eventually wearing through and parting that halyard. With the spinnaker halyard gone, and this year with it all "outside", the snapping is gone. (Clearly that was bad.)
2/ Some of my sails are too long in the luff (and some not), so the old Harken furling mechanism bangs right up at the top of the forestay with still a little looseness in the sail's luff. I'll deal with this eventually - sailmaker and so forth - but in the meantime I wonder if having virtually no halyard showing above the furling mechanism is bad for it as it furls. The halyard is supposed to be short, according to the Owner's Manual, and there is no wrap-stopper in this system.
3/ I came across a helpful thread
here saying to loop both runs of the spinnaker halyard around behind a spreader. I'll try that and hope for enough length of halyard. (Then I have to remember that it's there and handle it appropriately before and after using it ...)
4/ I use a snap shackle at the halyard-furler join, and I think that's because that's the way the boat came. Last year I actually lost the pin, and when I finally retrieved it, I took the pin from a new shackle and put it in - seemed perfect - and that way didn't have to cut the old shackle out of a beautiful spliced loop. But I do wonder why it requires a snap shackle. I attach that halyard basically once a year, and don't need to change it even when changing sails occasionally.
The photo is from when the spinnaker halyard ran inside the mast. I think it illustrates the situation better than words.
I know that's a lot, but if anyone sees any room for improvement in there, please let me know. I have a second foresail halyard, which has rescued the situation, but nonetheless, I have to fix this and stop if from happening.