I don't often disagree with Jack, but this time yes. If it was simply just forgot to throttle back the diesels, why didn't Ed just do that instead of the emergency stop and then putting the 844 in reverse and opening the throttle trying to fight the diesel pushing, there by stalling the drivers and skidding. If the MU box for the diesels was still in RUN, Ed would have seen that.
Nobody's questioning the integrity of the design of the MU box, but parts do wear out and break. Otherwise EMD would not have a parts dept!
On a side note, I hear the original MU box has since been replaced.