Kitchen Large Electric Appliances - agitator top half won't spin on GE Profile washer

I have a Ge Profile washer model number WPSE3120Y1WW in which only the bottom half of the agitator spins. The top half spins freely by hand in both directions during the wash cycle while the lower half seems to work fine. I read about the agitator "dogs" elsewhere on a Roper/Whirlpool machine but other posts say this GE doesn't use that system. I did pull off the fabric softener dispenser. I found four round plastic cylinders about 1" long with a hole through their centers that seemed to have become dislodged and replaced them in slots around the perimeter of the agitator shaft. I replaced an opaque round plastic cover which has a slight convex surface to it in the shaft over the plastic plus, then pushed the fabric softener dispenser back on. I started the washer and came back after 5 minutes into the cycle. Again no top half agitation. I pulled off the dispenser cap again, removed the round plastic opaque cover and found the four plastic plus floating inside the shaft and dislodged from their slots. I replaced everything again and this time the agitator seemed to work. I did notice that there seems to be about an inch gap between the bottom of the fabric softener dispenser and the opaque round plastic cover. This gap seems to allow that cover to float up and thus allows the found plastic cylinders to rise up out of their slots, causing the agitator,s top half to stop working. Is there another part that goes between the fabric softener dispenser and this opaque plastic disc to fill that gap and thus hold everything in place?

GE does not use that system, you have to replace the agitator