Hi Marcone,
Chris will help to you more that I could... but anyway I will try giving you a hand. I had an issue with the VCA of one of my channel strip. It is not the same, because your issue is tuck in the same place. I have read a lot about VCA´s because of my issue.
I think you have something wrong between the 611 lower bus card and 82E37 fader bus card. I would try swapping the ribbon cables which afects to the problematic position and see if the issue stays there. If the issue stays there, I would check lower bus card connections and all the 82E37 card tracks.
As I told to you, I am not an expert, but I share the little knowledge, in case it is helpfull.
Regards.
Oihan