Originally Posted by codprawn
The eye is a VERY heavy duty unit...
Apparently, not heavy duty enough...!
I imagine that this failure was caused by repeated side to side stresses caused by the opposing mooring lines.
Perhaps if you were to use one of this spiffy "shock absorbers" in the mooring set up, it would absorb some of the stresses.
I was surprised at how easily stainless bolts can be sheared off just by wiggling them back and forth a few times using use vice-grips or something. It's a great way to shorten a bolt that's too long once it's in place and the nut tightened...
I am doubtful of the swollen rope theory as well. Assuming you aren't using cotton or hemp lines, I just don't think that they're would be enough water absorption in synthetic lines to cause this, even if it were possible.