This might sound a little elementary but make sure the connecting rod is properly seated on each pedal, make sure the tension rods on the length adjustment are secure. If it's an older pedal then the connecting rod may have worn joints, this happened to mine twice over a long time. Rotate the connecting rod with your hand and see if there's a delay in the movement of the joints, if so then replace the connecting rod, and maybe look at using something from another manufacturer (use the Z link from the demon drive if you can).