Maybe this is a common problem and everyone knows about it, but just in case, there is an easy fix for this.
There are four screws that attach the machine's chassis to the body, and at each of those mounting points there is a rubber grommet. The rubber grommet cushions and dampens vibrations, but when they compress over time and end up looking like this:
Then the chassis drops down in relation to the body, and the rubbing ensues.
I just used a standard 1/2" rubber automotive grommet, and the problem is no more!