I purchased a Spyderco Chokwe knjfe and if you open it normally with your thumb it will close fine, But is you flick it open it is difficult to depress the spring so the knife can be closed. The faster you flick it the harder the spring is to release. My question is the knife defective or not. I can flick open my lock back and liner lock Spydercos with no problem but not with this one.