USB Controller

I recently purchased a Tomee USB NES controller and have run into an issue where the D-Pad can be a little touchy. When pressing one of the directions the controls will sometimes veer off in one of the other adjacent directions. For example when pressing down, character goes down then veers to the right then down again, all while holding the down direction on the d-pad. The emulator is FCEUX, I got similar results on other ones though. Any suggestions are greatly appreciated.