I have a WD electric washer model WFW9450WWOO and keep getting the F71 error. Sometimes if I unplug it, it will work again. Today it didn't. Appliance guy got the door unlocked by taking the top off, and somehow the washer started and finished a load, but he said I need to replace a board that's $500 for the part. He said he didn't know how to do a diagnostic on it. Looking online, I see a user interface board, a central control board, and an MCU unit. YouTube videos show the MCU being replaced for an F71 error. The drum rotates, so according to your info above it says replace the user interface board. I'm totally confused as to what should be replaced and how to diagnose what the actual issue is. Any help is appreciated. Thanks.

I am going to do you a big favor. Yes you need to replace the interface boards if the wash tub rotates back and forth which is good news for you as you can get the set of boards in good working condition for that model on eBay fairly cheap. The link below is a listing on eBay for the interface boards you need. Both boards you need are in the listing for less than 30.00. Please remember to dontate using the link at the top of the site. Thanks.

https://www.ebay.com/itm/183962893887?hash=item2ad50afe3f:g:wcgAAOSwZH1eKK6g