Tested with horizontal dispensed fireworks.
Linked issues
duplicates 1
Comments 2
Thank you for your report!
We're actually already tracking this issue in MC-173272, so I've resolved and linked this ticket as a duplicate.
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This is demonstrated in this video at 10:06 several times
https://youtu.be/So2RlXZ9vkM
One could build a dispenser (a block above the ground), fill it with rockets and then build 2 target blocks and 2 redstone lamps stacked on top of eachother(lamp on lamp target on target, the dispenser facing the target block) a distance away from the dispenser (I have not witnessed testing that has been done in close proximity so I do not know if this glitch would still take effect if it was much closer I don't know exact numbers but I think 16 blocks should be enough) some times the top lamps will trigger, sometimes the bottom will trigger and sometimes neither will trigger.