still getting F21

So frustrated with this washing machine. I infamously get f21 atleast 4 times a month. I have paid the service repairman more than what it would cost to purchase a new one. Could someone tell me how to fix the last part of the cycle. At bout 4 min left in the cycle I get f21, clothes a re soaking wet , already tried drain and spin, rinse and spin and  still will not drain   rjpearson@att.net