Top Spinner not spinning on Whirlpool DU1055XTVQ0
I have a Whirlpool DU1055XTVQ0 that is spinning both the lower and middle spray arms, but the top spinner at the very top of the cabinet is not spinning. It is getting water supplied to it as I can see it spraying out the spinner holes. I have pulled everything apart and cleaned it very well, with no improvement. Any suggestions as to what may be the cause of no spinning up top? Thanks!