Rob, I applaud you keeping your sense of humor . :B
IMO, i think its a rail adjustment as well. It could also be that the rails were not installed square to begin with .
I have been a helper at my friends rv shop and i can tell you, slide structures are weak . They lack real good structural support.
Think about it, there is very little room to install substantial headers and side supports .
Are you able to get under it while a second person moves it in/out , just enough to make it squeal ? You could use a long metal rod as a stethoscope to pinpoint the where the squeal is coming from. Touch the rails, the motor etc, if you have access .
When any rv is on a dealers lot, they never make sure the units are level. Then they demonstrate to potential buyers how great the slides are by deploying and retracting them many times. Being it's a weak structure, being off level really stresses all the components of a slide. They destroy them , it's like buying a used/new rv.
If you buy a new rv, order it new , when it arrives, get it off the lot asap. A good salesman can destroy any rv in a very short time. :B