What I expected to happen was...:
Piston should retract like it normally has in the past.
What actually happened was...:
The piston would remain extended until I gave it a "block update" by either removing a block next to it or placing one next to it. (There was no nearby power source for the piston to remain powered by)
Steps to Reproduce:
(SEE PICTURES BELOW FOR A MORE IN-DEPTH LOOK. It is somewhat hard to explain)
1. Place a couple pistons facing downwards in a 7x7 grid, with 1 block of air between each. (4 pistons with 3 blocks of air)
(note: the "grid" is more of just to cover more of an area to show that only certain block areas create the glitch piston)
2. Build a "pitchfork" above the pistons to connect them all by redstone (see pictures below for exact example)
3. Turn lever on, all pistons will power perfectly normal
4. Turn lever off, all pistons will de-power, but some will stay extended. (Pistons that stay extended will actually vary based on location of the build).
Note: This is a singleplayer world with NO MODS installed at all, and a brand new generated minecraft map. I discovered this little glitch/bug while playing on a multiplayer server building a redstone puzzle minigame for the players. I had originally thought it to be something with a plugin server-side but after testing in a singleplayer world I found it to be a glitch caused by 1.6.1/1.6.2 version of minecraft. It had worked perfectly fine in earlier versions (I had a similar build in 1.5 that never malfunctioned like this)
1st image: showing the grid
2nd image: Showing the "pitchfork" and redstone
3rd image: Showing the "powered" piston with no power connected to it
4th image: Different location of "glitched" pistons showing how more of them glitch.
5th image: Overhead shot of 4th pic to show no redstone is powered.
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kumasasa
Can you ZIP or RAR your world and attach it here ?
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Looks like MC-108, but then with powered redstone instead of a switch. tested it, and this works with all power sources currently.
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I've been having the same problem since 1.5.
The bug seems to be depending on direction and coordinates and weirdly sometimes depends on whether there is another redstone wire connected to the powering wires 3 blocks away and similar stuff.
The bug is independend from the gamemode and occurs in both single and multiplayer.
You can reproduce it by creating any world and placing:
cobblestone at x6.5 y7 z0.5, x6.5 y7 z1.5 and x6.5 y7 z2.5
a piston (any type, facing downwards) at x6.5 y6 z0.5
redstone wire at x6.5 y8 z0.5 and x6.5 y8 z1.5.
Then place and remove a redstone torch at x6.5 y8 z2.5.
Please confirm.
Unfortunately I have noticed this bug disabling some old adventure map riddles and two of my mashines, so I hope you can resolve it.
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Rebuilt your construction, Richard. I turned it into a cross-shape, the piston being the middle, a redstone wire in the other 3 directions as well.
It didn't depend on the direction, but putting the torch 1 closer or 1 farther away did matter. As far as coordinates go: so far I haven't seen any exception.
Do note: redstone causes a block update farther away than it should (MC-26014, guess I'll make a seperate report for it as it started out very unclear), so do mind your redstone for this.
I'm kind of actively researching this issue, as it caught my interest.
What seems to be the case: pistons NEVER retract or extend without block update; it's just that redstone causes it in every other case. (unless the switch is near the piston or when the redstone is connected to the piston without block between it)
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The bug also happens when activating a piston. Here is how to reproduce in any world, independent from the location:
Place a redstone torch. Place a piston (any type, facing downwards) 2 blocks below the torch. Done.
You can now place/remove redstone wire next to the torch without the piston noticing. It will only react upon a block update (e.g. by placing a block next to it).
Please confirm this bug.
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Richard, I've thought it is a bug for a while, but Mojang and a lot of users found it better this way. (for making block update detectors)
Do mind that redstone turning on/off does induce a block update (and at a bigger range as well as described in MC-26545).
Though as far as confirmation goes: Confirmed. (it's issue MC-108)