I've been following a tutorial, and one of the steps involves applying an x vector to the player sprite which has the platform behavior. However, after seeing that the x vector wasn't doing anything, I tested it: I made an event which would set the player's x vector to 900 when I pressed the M key, but doing the M key did nothing. I did the same with the y vector (which was working fine before), and saw that it correctly applied the vector there.
tl;dr: Actions are refusing to set any sort of x vector to the player.
Is this a known problem? If so, can you tell me what's going on?