This bug is present only with the Improved Minecarts experiment enabled.

Minecarts eject mobs incorrectly. The order of adjacent blocks is rotated 90 degrees clockwise from normal when the minecart travels east or south (rear, front, left rear, left front, right rear, right front, left, right, relative to direction of travel). When travelling north or west, the minecart ejection check order is rotated 90 degrees counterclockwise from normal (front, rear, right front, right rear, left front, left rear, right, left, relative to direction of travel).

Normally, the order is fixed relative to the direction of travel, regardless of what direction the minecart is travelling in (always right, left, rear right, rear left, front right, front left, rear, front).

To reproduce: Re-build the set-up in the attached video.