Take filter out of top of agitator. Down the bottom of the agitator tube you will see a hexagonal bolt head. Use a 10mm socket on a long extension to reach it. Do not try to over tighten it. If you do and the head breaks off you will have a major problem, also do not try to loctite or super glue the bolt in or glue the agitator to the shaft. If you do and need work done in future the service tech will not get the bolt out. I have struck three like that and have had to smash the agitator to get it off.
Lincoln Appliance NZ, December 2019