Floating inputs are changing state

[oyvind@kinsey.no]

so it's wrong, you have not connect DC terminal, that's why i need to see photo.

I have reviewed the schematic and verified that when I pull the inputs to ground, they do trigger. The board has exactly 12v input, and the INPUT_Dx terminals are floating at 11.6ish, which seems reasonable given the forward voltage drop in the optocoupler. 

What DC terminal needs to be connected here? 
The terminal not connected would electrically show up identically as an open switch (just with less noise due to the 'antenna' being smaller).