Do you have a Strong Track system on your mast?
I installed our system three or four years ago and I've been plagued by the repeated failure of clevis pin rings breaking and allowing the pins to work themselves out while under sail.
My usual fix up until now has been to use stainless safety wire in place of the rings.
But today (after a phone call to the manufacturer) I've replaced all of the clevis pins & rings with #10 panhead machine screws & nylock nuts - which is how the manufacturer is suppling the kit now-a-daze.
Total cost was less than $20 USD and I did it by myself in under two hours. I didn't even have to hoist the sail any more than to ease the weight enough to get a screwdriver between the slides. Too easy!
Only time will tell if the problem is solved... but I thought it's a tip worth sharing.