Couple times a day I have to   put a  row unit with  the steel  bushing  back 'on'..

 most of the time,  the  'keyhole'  that  holds  the bushing is sprung open a tad,  but most of it is  the  sheet metal slots   that keep the opener  positioned  side-to-side    has been bent.   quick  whack with a hammer on either of those spots  and it's  good to go. 

I always thought the  springs that hold the bushings in were a little on the light side too.

I can't imagine the grief  poly bushings would give!