I actually had this issue before in A20.1, I think. The fences just wouldn't work sometimes, and the console would pop up with errors in red text if zombies walked through them (they still shocked my friends, but would oftentimes not shock zombies).
Take all of your batteries, engines, etc. out of your powered components, then have the server host delete their power.dat file. Should be in \Saves\WorldName\. The game should remake it when he next restarts the server. You'll need to rewire everything back up again and place your batteries/engines back in their respective banks/generators, but the problem on my server was that file got corrupted and this fixed it, for me. Perhaps that will fix it for you too.