I was building a diagonal of downward pistons to push some other pistons on top of glowstone, and happened upon this.
I powered all of the pistons from above using a zig-zag of redstone and a wooden button. Each piston has a solid block directly on top of it, and each of those blocks are being powered by redstone dust on top of them.
The result was that for the pistons being powered by redstone power level 9+, there was no problem. Those extended and retracted as expected. But two pistons at the end are getting stuck consistently. They are powered by redstone power level 7 and below.
The pistons that stay extended are in BUD mode. If I place a block next to them, they retract. But it makes no sense why they would lock out in BUD mode, and only the ones on the low-power half of the circuit. Very strange.
I've attached screenshots, which also include block status data of the redstone while powered.
Again, to clarify, each piston has a block powered by redstone directly above it. They do also all have at least one block powered on the upwards-diagonal, which is a known quasi-connection configuration, but only the power 7 and below pistons are stuck.
I can provide the world upon request by a Mojang member if they cannot reproduce on their own. It is only a small creative world.
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Confirmed as being in 14w30c. Just as before, it is the last two pistons only: all others do not enter a quasi-connected BUD state.
Replacing every other block with an upside-down slab (leaving the full blocks above the pistons) solves this problem, so it seems to be the classic diagonal BUD, but power-level dependent.
Sorry for the delay, I was cooking.
Is this still a concern in the current Minecraft version? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases. If this has been done, we can reopen the issue.
Keep in mind that the "Resolved"-Status on this ticket just means "Answered", and that we are waiting for further information on whether this issue still exists or not. We will reopen it as soon as the requested information has been delivered.
Ticket resolved as incomplete, because no answer in a reasonable amount of time (1+ year), if it still happens, please update the ticket.
This problem still exists in recent version (I tested in 1.8, 1.14, 1.15.2 and 20w18a), and I find if the redstone dust above the solid block above the piston, has power level 2 or 4 or 6 or 8, then this problem would arise. Under other power level the piston would not enter BUD state.
The setting to see this problem is a little critical. The piston should be placed under a solid block, not beside(at same height). piston should not be placed against another piston that is controled by the same circuit. Transparent block like glass also prevent piston entering BUD state.
It also works for dispenser, dropper.
it actually happens with all even powers, reported as MC-196820
I can confirm that this is a bug. The last 2 pistons are supposed to deactivate, and not get stuck.