I have the same gap at the top of the bracket. I tried something really simple today - I stuck a stainless lock washer in the gap from the top. It went in about halfway and completely eliminated the slop. I was afraid i was going to have a hard time getting it out afterwards but i was able to remove it no problem with needle nose pliers.

I have to remove my platform every time i put it in the garage so I didn't want to do anyhing that would be hard to remove.

Guess I'll keep doimg this until i find a better way.