While the player is mounted on something (boat, minecart, horse) and a long-distance teleport is performed it will cause the surrounding chunks to be rendered very weirdly. The chunks that are supposed to be there aren't there (they refuse to load) and the previous chunks that were there appear to be there but aren't. If the teleport is performed again then the correct area will load, but the player will have no interaction.

Steps to reproduce:

Mount something (boat, minecart, horse)

run /teleport ~1000000 ~ ~ (or some large number)

-game bugs out