At the start of the game we are usually in the middle of the standing stances so begin by pressing ctrl+W to stand up fully straight (top stance). Then ctrl+S two times to go to the lowest standing stance (just before high crouch).
Now move "W" and press "C" to go into tactical stance with your weapon drawn. Press "X" (main stance button for crouch/stand) and you will notice you can only go down, but not up again during movement. If you stop you can go up and down as you please however.
Now stop and ctrl+W up one step (middle standing stance) and go into tactical stance "C" while moving again, and you will be able to crouch/stand "X" properly again.
I dont think this intentonal, but missed alpha style.