Problem with terrain collisions.

Hi!, Here is a game I am making for a schoolwork, you have to opened and press P as usual to start the third scene, the problem is that in some polygons of the terrain in this scene, specificly on sectors in the green part, below the mountain, the player collisions and the terrain collisions are being calculated wrong, and the player fall off the floor. Do you have any how can I fix it with some trick?

move with WASD, Shift to run, Space jump, and zoom with mouse wheel (bonus: if you get closer to a post, and you press E you can climb it :p)

Dropbox is a little strange in its user interface right now, you have to close the login box, and the press download although it darken.
https://www.dropbox.com/s/0shnfs9bj1ax2te/Don%20Bosco%20The%20Game.zip?dl=0

Why don’t you try to use the distance constraint actuator and disable it while the player is jumping.

I didn’t know this controller exists. I will try it, but I was trying to keep the game with the less number of actuators, sensors and controllers. Can you tell me why is this problem of collisions happening if I have the steps and substeps of the physics calculation at max level? Thanks again!

I have never put the steps and substeps of physics that high.I have never needed it.I think it is a limit that the blender game engine has.