The only thing I can think of, off the top of my head, is you're going to have to tighten the spring for the left pedal. I had the same problem with my Iron Cobra, until I tightened the spring. Now, it doesn't do it as much. The only pedal I have played, that doesn't do that, is the
Pearl Demon Drive Pedal. I will pick that up in August/September.
So try tightening the spring for the left pedal. It might help.