When sticky/regular pistons push redstone blocks, they don't retract upon being "turned off"!
What I expected to happen was the piston to retract just like normal!
What actually happened was, even when I flicked the lever back to "off", the piston stayed up just because it was pushing a redstone block.
Steps to Reproduce this bug:
1. Put a piston behind a redstone block
2. Use a switch to make the piston push the redstone block
3. Turn it off, it won't, just because it is pushing a redstone block
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Thank you for your report.
However, your ticket has been resolved as a duplicate.
This issue has been linked to the original bugreport: MC-108. You can find or add further information on that report.
Please search before reporting any bugs, as it's likely that one exists already.