Sticky piston adjacent blocks bugging mobs

I had a trap (created in 1.9 in a 1.9 world where i locked skeletons in a small area and i used sticky pistons to hurt them to low hp before dealing the killing blow.

After updating to 1.10 when i do that skeletons get bugged inside the cobblestone and get hurt to death unless i mine the cobblestone to free them.