with the elytra equipped several things can cause an "Invalid move player packet received" error, such as
using a firework while looking straight up
using a firework THEN looking straight up causes an error when it explodes
flying straight up, then reaching the peak of the incline causes it (it appears to shoot me towards the ground at great speed also)
or if look straight up while falling straight down
it appears to happen when only moving on the Y axis
below is an image of the message