Even idle dupes won't apply new valve setting if the valve is built "wrong". The "wrong" seems to be "any gas enters the valve before its setting is changed for the first time".
Safe approach to build a working valve seems to be:
- Build the valve and two unconnected pieces of pipe under its inlet and outlet
- Change setting of the valve, wait until a dupe performs the change
- Connect pipes under the valve to the rest of the circuit.
Probably safe approach to build a non-working valve:
- Build a circuit with at least a pump and a vent
- Let the circuit work
- Deconstruct a piece of a pipe between pump and vent when there's still gas in the pipe
- Build a valve in the middle
- Let it work for a while
- Try to change setting of the valve
Similar or the same issues appear there to be with liquid valves.
See description above