OF course since I'm not there this is all shooting in the dark but, how bout
the rollers on that side. Are they all rolling easily? ANy of them hanging
up?
What about equal and opposite reaction, maybe the other sides tension is off
a bit?

I have old wooden doors right now (getting ready to changover to new
ones shortly) when the right door cocks I just give it a "jerk" to the side
and it levels out.

What about where the turn is? are the turns level with each other? I
think thats where my problems lies, the tracks are a bit loose and when the
one side moves is when it "cocks"?

I hope I'm helping, if I could see it I may be a better help

RIch