If you sink to the bottom of a lava pool with elytra equipped, and then press the jump button once, your character will flip upside down, and the elytra will open, if the player then holds the jump button they will rise out of the lava upside down, however once they leave the lava they will continue to move upwards, until the jump button is released, when they player will fall back into the lava. This issue does not happen with water.