I'm sure you already tried different sockets right?I had 1 socket that the volt meter would not stablize to get a voltage reading.Nothing on that socket would work well and back then all I used was a RCBS 10-10 beam scale.Charging batteries were a no go on that socket.
I changed the socket and problem went away.
May not be helpful to you but just a thought.
I changed the socket and problem went away.
May not be helpful to you but just a thought.