Bad shifter feel
 

So I bought my 370z nismo used last year at around 25,000 miles, and I was informed the clutch was replaced when I bought the car. Over time the shifter (or it's my imagination) seems to be feeling worse, more clunky and rough. I've had the transmission fluid changed with redline mt-85 a few months back and its made no difference in the feel at all. I've been doing some research and apparently there's a lockout where you have to physically press down on the shifter to enter reverse? I've actually not known this, as all I have to do to enter reverse is just push straight right and then down to reverse (although with a bit more force than it would take to enter other gears). Is something messed up which is contributing to my really poor shifter feel and missing reverse lockout?

I'm far from an expert on this, but having had my shifter apart when I installed my short throw shift knob I'm guessing someone at some point installed an aftermarket shifter kit in your car and went back to OEM later.

I'd open it up and take a look. I don't have pictures, but there is a lockout plate that may be in the wrong position for you. There is a DIY thread on installing a short throw shifter which can walk you through the process.