To reproduce, use a firework while gliding to get the boost, and immediately save and exit. Upon re-entering, the firework will not be boosting you anymore and just shoots up into the air.

Note: To not cause strange situations in which the firework continues flying when the player logs out and then once he logs in again teleports to him, it would probably be good to remove the firework / save it with the playerdata and then load it again when the player logs in.