WTW5000DW off balance during spin

Our Whirlpool WTW5000DW washer is 2-1/2 years old and gets fairly heavy use (6-8 loads/week). It works fine for most loads but occasionally with towels or large sheets it goes horribly off balance during the spin cycle and jumps all over the floor until we shut it off. There are no screeching or grinding noises as some others on the forums describe. It’s just off balance. I do believe it’s sitting level but will check to be sure.

Reading here I can find several other possible causes. Which is the most likely problem? Suspension springs? Tub suspension pads? Shock absorber or centering springs perhaps? Help! My wife is tired of having to run from the other end of the house every time it goes wonky.