I have had problems (actually most of us have at 1 time) with my ring disconnecting on several boats.
my suggestions are:
try rotating the mast the other way ( after 2 years of struggling with my TheMightyHobie18, i found rotating the mast the other way (even thought it was opposite what was recommended) worked first time
try attaching the halyard differently to the ring (turn it around)
purchase a new / different ring.. last time.. i had problems constantly.. i purchased a Murray's Aussy ring... no more problems even though my old ring was also an aussy ring, but slightly different