Why are you setting the player Platformer speed and vector x at all? This creates unnecessary movement.
It's the background that needs to move, not the player.
Keep platformer speed to 0 and don't set vector x, just continually set player x to 105 as dop2000 suggested, although you could put it in inverted Is falling condition, so the player falls off the bottom of the screen.
Here's an example based off an edited version of the bundled auto-runner.
Note: the example also uses 9-Patch platforms that lerp move, which I find look and perform better than bullet sprites platforms.