When doing /tick sprint (60s, 1d, 3d) and then trying to get into a one block gap or to use elytra in such ways that cannot by done with player controls and no help from blocks, the game will lag and you will get stuck in a non-existent block, forever teleporting about 1/20 of a block up every half second. This is fixable with /tick sprint stop or /tp ~ ~ ~5 (or tp to a location that isn't close to many blocks) but even still, its a very annoying bug.