Pistons don't extend when a block is broken and their limit is now under 12 or 12.

This means that when the Pistons are powered, but before that the blocks are more than 12, which the Piston push, the Pison does not have to go out even though it is powered. This means that there is no block update on the Piston and thus do not push it.
You can work around this if you power the Piston again.

When you are above the max block limit of Pistons the pisons cannot push (On the right there is a normal piston and on the left is a sticky one).

 
But when you remove one of the blocks the pistons do not extend.
 

 
I fixed this issue by turning the redstone of and on again, but this is not the best thing to build in big redstone contraptions.