sorry to have you join the Artistic Blues Club!
my encoders seem to be fine. did you try putting a washer in between the screw and frame? also if you put white out on the encoder (just a little bit) you will be able to see it move much easier.
think we've all learned that sales people will say anything to make a sale!
try talking to the maker of the table...Grace Co. was wonderful in getting me an upgrade for the table i have.
Good luck...i have someone coming out on tuesday to help me with mine.