If swimming underwater with Elytra on and a Trident with any level of the Riptide enchantment, when I look up, hold the RMB (trying to throw the Trident) and then hold SPACE, the player will start to fall down, the Elytra will sound and after a few moments it will kick you out because: Invalid player packet received (or something like that). If I try to open the world once more, it may happen several times without me doing anything.

It happens to me in this particular situation. It may be happening in other situations, too.
Sorry for my bad English.
Henry Novak