Pistons do not update properly when powered from above by redstone dust in some cases. It seems that if a piston is powered from above by a redstone line (redstone on top of a solid block on top of a piston) it has a chance (locational) it will not retract after being de-powered. Using a comparator, a 1-redstone-tick pulse, or a redstone power level of 15 seems to resolve the issue. See the coordinates and redstone layout in the video to reproduce the issue.