One of the most useless purchases of my life. I bought an endura pro, the ultra-nav (the red nub in the middle of the keyboard) doesn't work properly: it moves

One of the most useless purchases of my life. I bought an endura pro, the ultra-nav (the red nub in the middle of the keyboard) doesn't work properly: it moves at different speeds depending on whether you're moving towards the right vs left. It drives me crazy. The problem seems to be that it gets stopped by a key and doesn't get tilted enought to trigger pointer acceleration. I'm supposed to erode a key somehow... To allow the lever to move a bit more, but it's a dumb solution to a problem that shouldn't be there in the first place.