First, check the adjustable feet. They may not be way out, but they're out of adjustment at least enough to let it vibrate and walk. Next, screw a cleat to the floor on the side of the machine toward which it walks. Before fastening, glue some scrap I/o carpet or felt padding to three sides of the cleat. Screw the bare wood side to the floor. This will prevent the cleat from damaging the washer.
John & Diane, fulltiming since '12 02 DS40, FL, Cat, '04 Element NHSO RVM103
John, Diane, and Lincoln, the guard cat. RVM103
Fulltimers since June 2012
2002 Dutch Star 40, Freightliner, Cat 3126, 2004 Element