Characters clipping through colliders?

I’m making a game where we build the levels out of cube-shaped “tiles,” somewhat similar to Minecraft. Each tile has a cube collider, and as far as I can tell, they match up perfectly, because each cube is 1x1x1 (plus a small plane on top for the grass or other ground texture). I’m finding, however, that characters are able to clip through the walls by running at them long enough. The characters have box colliders on them, and I’ve set collision detection to Continuous Dynamic already to no avail.

The most consistent ways I’ve found to get them to clip through is to run at a corner–like where open ground is bounded on two sides by wall–or an area where something is sticking out of the wall.

Any idea why this is happening? I was worried about the individual box colliders on the tiles, but I can’t figure out any other good ways for the ground to have colliders when I vary the terrain heights.

Are you moving your character by transform or by rigidbody?
if you are moving them via transform they will clip through the collider, change over to physics-based movement and update it in fixed update.