My washing machine is below grade, so is dependent on a sump pump. both appliances have been plugged into the same 3 prong duplex outlet, for years. The sump pump stopped working, and after cleaning it, and some basic trouble shooting I moved the sump pump to the outlet the washer had been in. Presto! it powered right up. But then I tried the washer plugged into the outlet that no longer runs the sump pump, and was surprised that the washer runs fine, in either outlet. Easy solution, swap them but no! Because the shape of one plug is elongated and can't fit in the configuration that would supply power to both. I'm tempted to by a little extension and make it work but entirely unsure if the issue might indicate something dangerous, like the ground not working. Any ideas? Should I replace the whole socket? Thanks!
Yes you should replace the socket. If there are any signs of heat damage on the plugs then you should replace those too.
It sounds like the contacts in the socket are going bad and are just about making contact with one plug and not the other. Socket contacts that are only just about making contact are not a good thing.