What I expected to happen was...:
Pressing Button-> Should avctivate both pistons, harvesting pumpkin and going back to retracted piston.

What actually happened was...:
Pressing Button-> Activated both pistons, but piston right-down-side didnt retract, though it has no signal anymore.

Steps to Reproduce:
1. Build like on picture
2. 2 diagonal pistons, Pumpkin below higher piston (so that Pumpkin will be destroyed), [horzontal-redstone line next to those pistons ?not sure?]
3. Need further more one thing that i dont know, i rebuild in Singleplayer and one construction is bugged, one not. Only difference is that one construction is one block higher. The other has 1 block space between ground and lower piston.

4. Try Savegame, already build bugged construction there.