I have a piston, getting no power that will randomly open. Sometimes when I power, then unpower it it will close, but that only happens 10% of the time.

I have been making a digital clock with redstone, and I had started making the minutes section. I made a memory circuit, Pistons spinning glass and wool in a circle, and discovered that I had on piston that would stay on, getting no power. I experimented and gave it power from different angles and every once in a while it would retract, but then as soon as it got power again, it would open and stay there. I also tried turning off the digital clock, but it did nothing, and I have put redstone where the piston was sitting, and it gets no power on or around the block. Note, The problem might be the fact that I don't know much about piston mechanics, but the nearest power is a torch on the green wool block across from the piston.

I have no idea how to reproduce the bug, as it seems to only happen on these few squares.