Once upon a time, long ago and far away. I worked for the stealerships, and since the instrument cluster repair fixed your symptoms at that time. They (dealership)will state that it was correct fix at that time and this new and improved problem... (well not improved) is not the same problem, even though its doing the same thing again.
So its totally unlikely if it is your VSM, that they will credit you for previous repair or warranty the VSM repair.
Hopefully you have a good working relationship with the Service manager at your dealer. If not, I would try to develope one. Maybe they will work with you?
Its been my experience that a dealership will try to avoid responsibility for mis-diagnosis, loose wheel nuts and general screw ups.
This is not bashing the competent, honest, hard working Technicians who work at the dealers there are many, but there are also idiots working there too and any good technician knows there are knuckleheads in the shop..
Regardless, lets give them the benifit of the doubt, play the devils advocate..
I have not looked at wiring diagram for that system, there are quite a few components involved and am sure there is some interface between VSM and instrument cluster so at that time, yours could have been cluster failure, but I doubt it.
I could be wrong and often am, since I would NEVER claim to know everything just what I have experienced.
Its possible that instrument cluster is in the same loop and causes same symptoms and that it has failed again in that case, I would insist they do repair free.
But for me it was the VSM. I called 3 friends one who has stayed at Ford and two others who have independent repair shops and before I could finish giving them the symptoms they all said "VSM" so this is a pretty well documented and predominate problem.
I was out of town with a little promotional business I have (see homepage here) and just told the old lady to take it to my buddy at Ford and tell them to fix it. Even thought I specifically told her to tell them to change VSM no questions asked they still clipped me for diagnosis fee!
I am going to dig into this more when I have time, but in the meanwhile I am going to spray the crap out of all the locks on all my F-350s as I own several. Ya might try yelling and screaming at dealer as I do, never helps me get anything, but I feel better when i leave.