The piston isn't being powered and it is pushing. No block around it, including diagonal, and it's just these pistons.
Updated version of https://bugs.mojang.com/browse/MC-120182. <-- I only use OptiFine for smoother framerate, but I disabled it this time
Environment
Windows 10 Home Version 1703 Processor: Quad Core AMD A8 3.2GHz 4 GB RAM x64 based
Jave 1.8.0_51 64-bit
No OptiFine or modifiers used
No resourcepacks/shaders used
Thank you for your report!
However, this issue is a Duplicate of MC-108.
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