[Gnawrocki1]

Are you sure you don't have intermittent leaking going on on your air bags?    There was a brand that had that occur due to the way the bags were connected to the end plates.  

By your description it seems like everything was good, and then all of a sudden it was not.  I don't think the 6 pack moves air that quickly as you made it seem.  However burping of a rear bag might do what you are saying, and you could have intermittent leaking that drives the inconsistency you are describing.

But what do I know?