ItsThatSpicymeme

Fix is to alter the texture ./assets/minecraft/textures/gui/sprites/container/bundle/blocked_slot.png to match the slot.png texture.

This is configurable in a resource pack under the same address.

Reply from @unknown:
While I appreciate additional input, you don't need to comment on every ticket now that Phoenix SC mentioned these tickets in a video. Thank you.

Can confirm bug affects 1.21, as well.

Confirmable via checking version .jar textures (./assets/minecraft/textures/particle), or via the /tick freeze and /tick step commands when launching a firework rocket.

Note that the bug is on the texture spark_4.png and not to be confused with spark_6.png, an (almost) identical looking texture, for firework rockets' sparks count backwards from spark_7.png as they fade out.

• This is due to the .json for end/killed_dragon does not contain a specific criteria for what dimension it is killed in.

• This is customizable with a Datapack if prefered.

//...  (comments aren't allowed in json btw lol)
      "conditions": {
        "entity": [
          {
            "condition": "minecraft:entity_properties",
            "predicate": {
              "type": "minecraft:ender_dragon"
            },
            "entity": "this"
          }
        ]
    //missing the following:
//           "location": {
//          "dimension": "minecraft:the_end"
//        }
      }

• This may be a bug, however it might be good to leave it that way, for if you accidently move it to another dimension and kill it there, you are still freeing anything under the Dragon's influence, and also so you don't need to kill it more times than you may or may not want to in order to get the advancement.

Game crashes on 1.16.4/.5 when cap is regularly reached (i.e. constant spider hisses). Turning sound off in menu helps to circumvent the issue when rejoining the world.