Desync when mounting an entity while sneaking

The bug

Double right-clicking quickly on a minecart while pressing and holding shift (press shift at the same time as the first click) leads to Minecraft thinking you are in the minecart while you are not actually in the minecart. If you move too far away from the minecart, it becomes impossible to break or place blocks, and pressing sneak causes you to be teleported back to the minecart as if you had just dismounted it.

To reproduce

1. Place a minecart on a rail
2. Enter the minecart and start sneaking at the same time
3. Quickly right-click / try to enter the minecart again
4. Walk away
5. Try to place a block
   → The block disappears again
6. Try to open a chest
   → You're unable to open the chest
7. Sneak
   → You get teleported back to the minecart

Video

https://www.youtube.com/watch?v=RYnnF3RXxRk