I have a column of 4 dispensers, all facing the same direction (to the right). For demonstration purposes, each is loaded with a different color of shulker box.

redstone setup

In the above screenshot, the dispensers are situated next to a 1-tick pulse generator, but not connected to it. By placing redstone dust on either the diamond block or the gold block, the dispensers are connected to the circuit so that the button causes them to activate.

If redstone dust is placed on the diamond block, all 4 dispensers activate.

redstone on diamond, all 4 shulker boxes spawned

If redstone is instead placed on the gold block, only the top 3 dispensers activate.

redstone on gold, only top 3 shulker boxes spawned

Since the redstone dust is not powering the dispensers, I'm guessing this is some kind of block update issue, but I don't understand exactly how it's working. What explains this behavior and how can I predict how the dispensers will behave inside of more complex circuits?

I'm using 1.13.1 Java edition.

  • Do the dispensers face into each other or away? If they face into each other, the redstone update order matters. – Fabian Röling Oct 5 '18 at 20:41
  • @Fabian They all face the same direction, towards the nether brick fences. – ApproachingDarknessFish Oct 5 '18 at 20:42
  • Is there even a redstone line on the bottom left? I see none. – Fabian Röling Oct 5 '18 at 20:53
  • There's no Redstone except for on the diamond block and I the quarts slabs. I'll post a better screenshot later. – ApproachingDarknessFish Oct 5 '18 at 20:56
  • And you somehow get the bottom one on the right to activate despite not leading a redstone wire to it? Are you abusing MC-108? – Fabian Röling Oct 5 '18 at 20:58

This is a block-update bug.

First, the yellow dispenser (color-coded by the color of the shulker box dispensed) is dispensed. Then, because the Redstone runs right into the dispenser, the red and green dispensers fire immediately after, which is why the red shulker is facing upwards while the others aren't.

Next, the blue dispenser updates. The fact that the Redstone is on the diamond block makes the dispenser think it is being powered while it is not. As such, it fires, and the blue shulker box gets dispensed.

This only happens because the Redstone is on the diamond block, 2 blocks away. Yes, this is a bug. I don't look into Minecraft source code, I'd just put the Redstone on the gold until it gets fixed.

| improve this answer | |
  • To call this a bug is questionable at best. The quasi-connectivity has been in the game for so long that you can hardly call it a "bug" anymore. – Chund Nov 4 '19 at 6:48

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