tauqua
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Where was the platform with the redstone. Redstone, since 1.5, will update the nearest block first, and so on, every game tick. Also, pistons can't push extended pistons. What I'm assuming happened was that the platform, which appeared to be in the middle, activated the top half first, therefore extending those before the pistons below them, so those couldn't extend because they were trying to push extended pistons, which are tile entities, so can't be pushed by pistons.
Perhaps those blocks were silverfish blocks, which spawn naturally sometimes and break evenly with everything?
Here's a video (gif) of this in action. F3 at the beginning shows specs/version in case that makes any difference. gfycat.com/AncientIncredibleHousefly