Why do multiple keyboard inputs stop playing an action? I have a simple character, who has simple animations. In the logic editor, I have a Keyboard sensor (W) > And controller > Action actuator set to Loop stop.

I did the same with another keyboard sensor (S). When I play the game and use W it's fine, and when I use S it is also fine. But when I press both of them (W+S) and let go of only one of them, the animation stops. 

This only happens when I wait for a second after pressing one (W or S) and then press a second. In other words, the game is fine until I press 2 of the functions at once. 

How can I let both W and S work fluently with Loop Stop enabled?
This is because an and controller requires all connected sensors to be true to pass a signal to the actuator. An or controller requires that at least one of the inputs is true.

Think of it this way: 


An and controller requires both sensor 1 and sensor 2 to be true.
An or controller requires either sensor 1 or sensor 2 to be true.


This is just boolean logic, see the wiki for more details.