I apologize ahead of time if this is a duplicate, but I tried searching for related issue, but was unable to find anything for the v1.11 release.

The issue is once pistons have been powered/extended by redstone dust from above, they are remaining extended even after the power has been removed. Three images are attached to demonstrate the bug. This same setup worked just fine in v1.10.2.

MC_Piston_Bug-Image01 - Shows the initial state prior to applying power.
MC_Piston_Bug-Image02 - Shows the pistons when power applied.
MC_Piston_Bug-Image03 - Shows the pistons still in powered state after power removed.