Second time l sailed my boat after buying it, but before going over it with a critical eye, the same thing happened. The boom and main-block detached itself.
The best time, the best place, 25kn winds 10 feet seas comind out of Mollolabah...
So l bought a 2mm cobalt drill bit and a roll of thin ss wire and drilled a hole into every shackle-pin head aboard a 2mm hole and tied it with ss wire.
Problem sold forever.