Under my sink is a working duplex electrical socket. My disposal works regardless of which of the two sockets it is plugged in to. The disposal has a grounded (3-prong) plug and this duplex socket is the only thing on that circuit breaker.
My paper shredder (which has a 2-pronged plug) works without hesitation when plugged in to other sockets but does not work at all when plugged in to this socket. The shredder is almost new, but just to be sure I have adjusted the prongs on the shredder's plug to move them to the sides to make sure they make contact with the (brand new) socket. I have tried switching out the duplex socket with a different new socket, I have tried reversing the white and black wires going into the socket, and I have tried working the shredder with the disposal plugged in and with it not plugged in. Again, the shredder will work in every other socket in the room except when plugged in to this particular socket. (Upon further experimentation, no 2-pronged plug devices work when plugged in to this socket.)
I have a multimeter but don't really know how to use it in case anyone needs me to use that to diagnose. What am I missing?