Setup: Have a player ride a minecart into a portal (can be nether or end portal).

What's expected: Once the player and minecart go through the portal, they are intact, and the player is facing the same direction as before they entered.

What happens instead: After the player rides the minecart through the portal, the direction the player is facing is always 90 degrees to the left of the direction of motion of the minecart as it enters the new dimension. (For example, if the minecart entered the portal facing positive Z, it would exit the portal with the player inside facing positive X.) When the player is riding any other entity (such as a horse or pig), this problem does not occur.