either physical obsticale and it's routing around or you are superficially watering and roots are turning toward greater moisture at the top.
really shouldn't have a huge gap in the medium like that. roots exposed to light will differentiate into stem and be useless.
you do not need to cut a hole in the bottom. if it's loose, push it slightly down and cover and shape it back to 1 piece of medium instead of 2 halves with a huge gap. When you irrigate, make sure you fully saturate
roots can burrow through some pretty hefty material. if you water correctly, gravity and moisture should keep it tunneling down instead of toward the surface.
keep it simple.. don't make it complicated.