Same deal here.. right side was a PITA to get on and off, left side fit like a glove. I believe the problem with mine is that the nut welded on the back of the support is not exactly aligned, so it's maybe a degree or so out of whack. What worked for me was to put the post on the front, put the bracket only on the front post, swing it up a bit and push it towards the bike to bend the metal just a hair. After a couple of tries, it fits perfect now.. slides on and off like butter on a hot tin roof.
Cheers,
Brad
