The bug
When you fire a firework from a dispenser and the firework hits a block, the firework slowly moves in the mid-air, even there are blocks that should the firework hit. When it finally hits a block and you remove that block, it gets completely stuck.
How to reproduce
Place a dispenser
Place firework with flight duration at least 50
Activate the dispenser
Wait until the firework hits a block
Remove that block
→ ❌ Observe that it got stuck in the air and slowly movesWait until it hits a block
→ ❌ It is now COMPLETELY stuck
In case you don't know how to give yourself that long flight duration rockets, the command is:
/give @p minecraft:firework_rocket{Fireworks:{Flight:50}}
This is not happening in 20w45a