When two minecarts are on a collision course with each other on ascending rails, instead of colliding and changing directions they just phase through each other.

Reproduction Steps

• Build an ascending rail track
• Place one minecart at each end
• Push one minecart downwards and the other one upwards

Observed Results

• The minecarts phase through each other
  minecart bug.mp4

Expected Results

• The minecarts would collide with each other and reverse directions.