I understand that wireless redstone was removed due problems it was causing with the server.
It seems that a new plug-in addition is causing an oddity with the pistons-
several players working on a project called this to my attention;
I only witnessed this with the horizontal sticky pistons though. When a power source is applied the piston protrudes in two directions, horizontal and down. The horizontal piston behaves normally. The vertical piston, will not retract after power is removed. They are solid, and can be broken from the piston base.