I have seen an issue mentioned about pistons being powerd diagonally and from 2 blocks above. this is more specifically about problems with pistons and redstone blocks. it seems that when a sticky piston (and I imagine normal pistons to) push a redstone block in any direction, they can the retract when no more power is being sent to them. with the exception of when the piston is pushing a redstone block up. when pushing a redstone block up the piston will remain extend even when power is no longer hitting the piston.
I have tried hitting the sticky piston with power and turning off the power again, but nothing other than breaking the redstone block seems to work.

also, when sticky pistons are placed side by side faceing up, and a redstone block is place ontop 2 or more pistons beside each other, the first of the 2 pistons to have a redstone block placed on top will extend and then stays powerd by the second redston block on the piston beside it, it will refuse to go down even when the redstone block ontop of it is broken.

it would seem that when the second redstone block is placed beside the first, the power of the second redstone block travels through the first redstone block and then down to the piston below it, and once that piston extends it would seem that second redstone block then continues powering that piston through the extended part. but that's just my theory.

but also, with 2 upward faceing pistons are side by side with a redstone block placed atop 1 piston, and redston power is sent through a repeater into the redstone block, both pistons extend. but I have only seen this happn in my world once and have not been able to re-create this last glitch.