A glitch in colliders.

Hello,
I have a huge static floor where my character walks on when all the sudden, my character stops and doesn't move anymore. I have no other colliders BESIDES the floor that it walks on, so, I thought that the first person character controller wasn't working properly. In the scene, I moved my character to a different spot on the floor while in the game, and it worked again. Then, after a while, it stopped. My floor cube is at position 0,0,0, and I noticed how my character stops walking and gets stuck when its x position is greater than or equal to the negative of the z position so I am thinking, maybe it has to do with the triangles in the cube. Sure enough, it has a mesh collider, but the 2 triangles that make up the top of the cube that the character walks on should be at level, so I don't know WHY that problem even occurs.

I am also having the same problem when I switched to using a box collider instead of a mesh collider. I had to create 2 separate game objects (one that renders, and the other with the collider) and attach a script that changes where the collider is depending on where the camera is in order to 'fix' this problem.