I used snubbers all last season guiding so they got used alot, and never had one break. I even snagged bottom once and the downrigger started letting out line before it snapped, so I think maybe your's got roughed up in the rocks a little or something. 3 other guides at the lodge use them too and they never had one break off like that either.
but one time, one of our guys snagged bottom while fishing on his own and it worked properly; broke off at the bottom of the snubber, so he was pretty happy about that.
Captain Dudds