A dispenser facing down to drop boats into water fails to fire some of the time when triggered by a remote or adjacent redstone signal (from button, torch, lever). The dispenser will fire a few times or just once before stopping. Repeated attempts to fire fail for as long as more than a minute. Getting closer to the dispenser seems to help but not always.
Have been in creative and survival modes. World is flat and biome is plains. Another dispenser within a few blocks is facing sideways and has not misfired once when triggered by tripwire hook.
Perhaps the problem is with the orientation being down.
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[Mod] Neko
Can you attach a screenshot? Most likely dupe of MC-108.
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Here is a version showing the bare basics with respect to Redstone. The dispenser works some of the time but then refuses to operate. No change is made except for the use of the levers to activate it. I can turn either lever on and off repeatedly and it may work at first for a few dispenses and then ceases.
I don't believe this is related the issue MC 108, since no pistons are involved and since the dispenser works as intended some of the time.
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Here's a video of the problem in action: https://youtu.be/9PLVdBabwlU
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The order of block updates combined with MC-108 is to blame.
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Could you please elaborate? In what way can one resolve this issue? How is the order of block updates affected and what can be done to make this dispenser function consistently?
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As well as being powered if a block adjacent to it if powering it, a dispenser is powered ifthe block above it is powered in this way, but it will only update its quasi-powered state if it is updated by an adjacent block update (MC-108). Block updates by redstone torches go 1 block in all directions IIRC, updating the X axis first, then the Y axis and finally the Z axis from smallest to largest coords. I hope this is of some use. Also please tell me if I'm wrong about any of it.
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Dispensers remember if they are powered or not so they don't trigger again while they are still powered. What's happening with your second lever is this: When you turn it on initially, the dispenser, knowing it's currently unpowered, is triggered and sets its state to powered. When you hit the lever again, the redstone line turns off. Due to the way redstone updates, the last piece of redstone dust actually turns off first. When that last piece of redstone dust is turned off, it sends an update to the dispenser. The dispenser still sees power coming from the penultimate piece of redstone dust, so it doesn't set its state to unpowered. When the penultimate piece of redstone dust turns off, the dispenser is not updated, so it doesn't set its state to unpowered. Activating the lever again will update the dispenser, but it won't trigger because it knows it's still powered.
You can probably fix this by powering the dispenser from the side.
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Why would a dispenser check for power at the second to last redstone dust? It should only be checking the redstone dust directly connected, or the dust connected to a directly adjacent block.
Here is another manifestation of what may be the same bug: https://youtu.be/0qobI4z8des I built a piston door for a minecart to pass through using three sticky pistons and a detector rail. In the first build, where the minecart travels east through the door, the pistons do what they are supposed to. A few blocks away I built an identical door for minecarts travelling west into the wall, but the pistons behave poorly - so poorly that they do not follow the rules of redstone mechanics.
Is Mojang ever going to fix these bugs?