when you say slop in the lowest gear I presume you mean up and down movement not side to side which would be bad. I am not familiar with the Harken you have but every other NEW winch that I have played with has up and down play in all gears AND drum. All forces should be applied at 90% (or actually 80-85) so this isnt a factor. If you have any side to side it would be bad. As you bearings appear OK I guess it would sudgest the brass tower is deformed.........
Seems unlikely with the way these things are built, man they are nice. Ive been playing around with "solid works" an engineering program and it is so cool to see how forces are distributed around different shapes. Low stress areas Kinda corresponds to where the cutouts are on the winches...... go figure