The bug

Teleporting into a one-block-high-space (specifically under a block with the potential to suffocate) will cause the player to be pushed horizontally, despite them being able to crawl in that space and as such not actually needing to be pushed out of any blocks they would end up intersecting.

How to reproduce

1. Place a block with a one block gap above the ground
2. Stand on top of this block
3. /tp ~ ~-2 ~

Expected results

The player would simply be moved directly down by two blocks and enter crawling mode.

Actual results

Alongside the above two thigns happening, the player also is pushed horizontally, possibly outside of the block's space and therefore exiting crawling mode.