It is not super weird, and not even surprising. Remember that any action code is executed many times per second (usually about 60). When pressing and detecting a downed key, even if you just tap it quickly, the code will almost always execute two or more times (it takes a lot of time in terms of computer speed for a key to be pressed and released). Therefore, you need another condition (the first being that the key is down) to regulate the spawning of the actor. A second condition that should work might be that no object of the type being spawned are currently in the world.