Elytra boost does damage

In Minecraft Better Together includes a bug that manages to damage you during an Elytra boost. It appears to be when you use a firework (not Rocket) you will lose health, while in the Java Edition, this does not happen. When you right click, it takes a bit and then BOOM, it takes away about 3 hearts. This happens in every direction you are pointed at. I hope this can be fixed in Minecraft 1.2.1, and thanks for reading.