Image 1st bug: The piston can be powered through an air block. (It shouldn't work)
Image 2nd bug: The two pistons can only be powered once with this clock. (It should work)
Image 3rd bug a+b: The piston can be activated, when the block below the red wool was updated. (It shouldn't work)
Image 4th bug: Both pistons are powered by the redstone. (Only the upper piston should work)
Image 5th bug a+b: The piston turns on, when it's placed on the red wool. (It shouldn't work)
Image 6th bug: Only the lower two pistons work. (All pistons should work)
Linked issues
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Comments 4
I can't believe that this is intended. Back in version Beta 1.7 the pistons worked fine. With this behavior it is nearly impossible to build small piston contraptions, without glitching as hell. R.I.P. pistons.
Please only report one bug per report. Most of the bugs you listed are caused by MC-108. The behavior shown in the first screenshot is intended, see MC-109266.