Hi Mark,
Hope you have an epiphany, and find the cause of your chatter. Sometimes when I leave something ( a problem), the answer smacks you upside your head in a day or two...
Where do you phyically locate the buttons for the DZ-1000's ??? Right by the switch it controls? on the fascia?
I am now currently re-visiting the block detection firmware and hardware. Not sure where I am headed with this, however it seems like it could be involved for sure. I might just get one detection block working then continue wiring the layout.
As far as your chatter goes, I have found that both inputs to the switch are held low so it tries to satisfy both at the same time. Cutting pliers come in handy for sure.