Why does agitator only work on Heavy Duty setting

My washer will not agitate during wash cycle if I use regular or delicate settings, but is works perfectly on heavy duty setting

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I didn't start this thread, but I have either the same problem or a similar problem. In the slower gentler speeds (handwash, delicate, regular) it turns on and off with quite loud relays clacking - it didn't used to do this except maybe on "delicate." It can't be running right. Any help?

Kenmore Washing Machine "90 Series" Model # 110.26901690

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