If you have a kicking strap system which uses an offset clip as show above (common on Winder Mk 3s), you would be well advised to check the offset clip for cracks on a regular basis.
I think the problem is occurring because when the boom is, say, let out to port (as in the photo), the tension in the kicking strap tries to rotate the clip clockwise, putting compressive loads on the left hand leg and tension on the right hand leg. The stress from the tension is most concentrated where the cross section in smallest (i.e. where the hole is) and the bend in the clip weakens it further. At the 2014 Europeans two boats were found to have this problem, in one case both legs were cracked.