When you place a trapdoor one bloc high at the bottom of the second bloc, open it, and then close it while standing below it, you get in the swimming position. The issue begins to occur in 19w14b. It stops when you swimm away from the bloc below the trapdoor.

I expected to pass trough the trapdoor when closing it.

But instead I get on the groung in the swimming position.

How to reproduce :

1) Place two blocs one above another

2) Place a trapdoor on the bottom of the bloc above.

3) Open the trapdoor and go on the bloc in front of the trapdoor.

3) Close the trapdoor