I discovered this bug when I accidentally shift-clicked my flight duration 3 firework rocket into an enchantment table. When I took the rocket out of the enchantment table, I realized it did not combine back into the rest of my stack of tier 3 rockets. Turns out, placing a flight duration 3 firework into a enchantment table reverts it into a regular firework (like the rocket literally has no tags on it. No flight duration, no extras, nothing. You can view this in the photo). I tested this bug with other fireworks (different flight duration, different colors, different effects) and they all had the same affect. One bit of information is that I was on a realm server, however the bug still appeared in singleplayer. Also, for this bug to occur, you need to shift-click a firework from a stack into the enchantment table. Individual fireworks will not succumb to this bug.