If a high speed minecart enters a nether portal sometimes it will spawn on the other side at the wrong location.
This is not the minecart simply moving out of the portal quickly as due to MC-275560 all minecarts moving out of portals are stationary for 3 ticks and indeed by running /tick step 1t 3 times you can see it is indeed stationary. Which means the minecart was spawned at the wrong location.

Reproduction Steps

Note: This is quite inconsistent. You may need to try a few times

• Increase minecartMaxSpeed to a high value
• Use /tick freeze and /tick step 1t to precisely follow the carts movement
  bug-demo.mp4

Observed Result

• The minecart spawns a few blocks away from the portal

Expected Results

• The minecart would spawn inside the portal