Shifter feel in 1st and 6th

[radare]

Now that I finally have PBT road worthy, I've put a few hundred miles on it. One thing I've noticed:

With my black and my red Seca II's, when I'm in first gear and I press downward on the shifter, the shifter will move downward as if its shifting but nothing really happens. Same thing with 6th gear. Pushing up on the lever will move the shifter but nothing happens since I'm already in high gear.

On PBT, when in first or sixth gear, if I press on the lever, its rock-solid and does not move. That is, in first, it wont press downward. In sixth, it won't press upward. The bike shifts just like the others in every other regard.

So which way should it be and why are they different?