Pistons will extend when a red-stone torch is placed on a block diagonally to it despite blocks passing the current and if a block is receiving power from a repeater and a piston is placed next to the block it will extent but it will cause any adjacent pistons to extend as well.
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...please use the search function to see if your bug has already been submitted. Currently over 53% of tickets are being closed as duplicate.
rakso101
Sounds like a duplicate of MC-108