Hard to believe this mission still bugs. but it does. Security Cadet after getting rifle from locker runs to target area, stops and his gun disappears. Game doesn't recognize you have equipped your rifle. After killing 3 Klingons in transporter room and reaching 71% on mission, there's no other enemies, and no way to restart the mission. If you unequip your rifle and relog, the last 2 klingons appear in the hallway and you can reequip your rifle and proceed.