In the whites and colors cycle, it is supposed to agitate in high speed for the first part of the cycle and then switch to slow til end of agitate. Have you tried agitate in all three cycles? (whites, colors, delicates). You can test slow speed by going to spin in delicate cycle which should be slow speed. To switch between agitate and spin, the motor direction is reversed. This is accomplished by reversing polarity of the start winding in the motor which is done through two sets of timer contacts.

I'm not all that familiar with drive/transmission of this machine. I would remove the belt and see if the motor operates in agitate mode to rule out a transmission problem preventing the motor from turning in agitate direction. If it still just buzzes with the belt off in agitate mode, it could be bad contacts in the water level pressure switch or the timer.

Eric