The issue I am experiencing is that a powered block 2 spaces above a POWERED sticky piston is causing it to not update to the unpowered state when the redstone power input is cut to the powered piston. If the block 2 above the piston becomes powered while the piston is UNPOWERED, the piston REMAINS unpowered. Also if the power to the upper circuit is cut off while the piston is unpowered and stuck in the powered state, it does not revert to the unpowered state.

This was tested with redstone dust, redstone repeaters, other pistons, and even just a powered piece of cobblestone with air underneath it acting as the block placed 2 blocks above the piston.

EDIT: For reference, the piston was placed horizontally, not vertically.