When I begin a cycle my washing machine fills with water, but when full instead of agitating it makes a really loud banging sound. When I open the lid I can see that it is simply not agitating, almost like it's not connected to whatever it is that turns it from the underneath (the agitator?). The agitator must still be moving, but somehow it's not able to catch the center piece to make it agitate. When I move the cycle to rinse it spins and drains the water just fine.

Do I just need to change the agitator? If so is it part number AP4027780?

Thank you so much for your help!