Shifter getting stuck?????

Whats up guys. a friend of mine just installed a new clutch in his 87 jeep wrangler. The problem he is having is this.....When the car is off you can move the shifter through the gears no problem. But once the car is on and you actually drive the car the shifter tends to get stuck inbetween gears. He said once it gets stuck if he lefts off the clutch and then depresses it again it comes loose.

Do you think he could have installed something in the clutch wrong? Or what could it be? Shift linkage?

yep, sounds like the clutch isn't disengaging fully. Will likely need to go back in and make sure everything was put together right.