Got a spinlock on the club Tiger and the Harken on the C2.
In my eyes, the spinlock looks like the better idea in theory, but disappoints in reality. Seems like its either always slipping or not 100% engaged, or who knows. Likely user error (dam crew) but it should be more fool proof.

Never ran into your issue. Did you have adequate tension on the halyard takeup? Might run the tail of the halyard through an eye further outboard on the beam? Just ideas