This happens both up/down at 8bps. If you lower maxSpeed to 1 the cart will now properly stop when going down, but will still clip through block when going upwards.

Reproduction Steps

• Build this setup
  
• Send a minecart up/down

Observed results

• The minecart continues to move despite that it's hitbox should have colided with the blocks above the track.
  

Expected Result

• The minecart would be stopped by the block
  (Like it does at 1bps when going down)