Having come from the other side (hmmm...that sounds like the punchline to a dirty joke) that is, having been the BOC tech who was dispatched to correct the problems caused by the VCA's, I can tell you that the most common troubles were fixed by simply by-passing the VCA whenever possible. The repairmen knew that, the foremen knew that, and apparently everyone all the way up the chain of command knew that. The VCA's were good for a lot of overtime, though.
