When a sticky piston with a block on its face receives a 0 gametick pulse it gets stuck, as can be seen in the attached screenshot. The sticky piston will remain in this state until it is broken. Powering and unpowering it or giving it a block update won't fix the piston. 

This does not happen to normal pistons that receive a 0 gametick pulse.

Sticky and normal pistons also don't get stuck when they receive a pulse of at least 1 gametick. 

This appears to happen in every location and direction. 

I attached 2 world saves. One world was created in 1.12.2, the other in 18w30b. Both worlds contain the same 4 setups (the other attached screenshot), to create 20 gametick, 2 gametick, 1 gametick and 0 gametick pulses. In 1.12.2, all these setups work fine. In 18w30b, however, the sticky piston in the 4th setup  gets stuck.

This bug is probably related to MC-135194