The cutter requires that the pivot bolt holding both halves together is as tight as possible while allowing movement. It's critical that there's zero gap between the jaws as they close, otherwise you'll have the problem you experienced. It's the same as with scissors, if you've ever tried to cut paper with scissors with a loose pivot you'll know the problem.

If the bolt is tight, it's likely that your cutter's jaws weren't properly ground flat on the inner faces - rare but could happen.