Command blocks retain redstone signal after powered once

When a block is powered it retains the output signal even after power is not input. I've tried turning it into an impulse command block to make it only work once, but the output signal stays, and it charges the next repeating command or prevents it from happening again if it is an impulse command. All commands are set to "Needs Redstone". I've also broken the comparators and replaced them, but it stays powered.