HI I have a lg wft502c fuzzy logic topload washing machine?

HI i have a lg wft502c fuzzy logic topload washing machine. The drum will not turn on the wash cycle the motor turns but back and forth but the drum wont engage. But on the spin cycle it will engage and spin the the drum. The actual agitator plate in the bottom of the drum came off and I screwed it back onto the hexagon metal plate in the base of the drum, it appears that a clip or something else may be missing from in between the base plate and the agitator plate which engages the bowl to move during the wash cycle???. I check the belt and this is still intact.

Any ideas??