Walking through walls collision problem

What I have is a house which is set to collide with a character by ellipsoid-to-polygon mode with a full sliding response. The problem is that the collisions don't appear to work some of the time. For example, my character can run across the floor and when he runs into the walls he usually stops, but sometimes if I hit the wall at a certain speed and angle my character just goes right through. This only occurs in certain places on the wall. I know it doesn't have to do with the radius of my character because no matter how I adjust that the problem is still there. This isn't a problem when I set the collisions to 'stop' response, but when I do this a different problem arises which is that my character can't even move when he's in the house. I've thought of dividing the house into two separate parts, the walls and the floors, and having the walls trigger a stop response and the floors trigger a sliding response, but this would involve going through every building model and separating the walls from the floor, which would be quite painstaking and laborious.So, can anyone think of a better solution to this problem or at least explain why this might be happening?