How can we fix this?

You need to take off the clean out plug and clean out the drain and filter. Here are some manuals: https://dl.dropboxusercontent.com/u/8010163/Understanding%20automatic%20washer.pdf
https://dl.dropboxusercontent.com/u/8010163/Whirlpool%20Washers.zip
https://dl.dropboxusercontent.com/u/8010163/Whirlpool%20Washer%20L-61%205th%20Generation%20Solid%20State%20Electronic %20Control%20System%20Service%20Manual.pdf
https://dl.dropboxusercontent.com/u/8010163/Whirlpool_WasherMVWC%2BWTW.pdf
https://dl.dropboxusercontent.com/u/8010163/Whirlpool-Kenmore%20washers.zip