Bug ReadValue() not updating when losing focus

I have a custom HID device talking to Unity through the new Input System Package (1.3.0). Currently the inputs are simply outputting to a display to show what is happening, using InputControl.IsPressed() or AxisControl.ReadValue(). Whenever the game window loses focus (in Editor or Standalone) these inputs are no longer updated and continue to report the same value although the Unity update itself is still working. Reselecting the Game window starts them updating again.
The values in the InputDebugger also stop updating as soon as the GameView loses focus, even if I just click on the InputDebugger itself.



I have looked thoroughly at the Input System Documentation (1.3 & earlier versions) and have tried multiple settings but nothing seems to achieve what I need, which is for the inputs to always update regardless of focus.

According to
https://docs.unity3d.com/Packages/com.unity.inputsystem@1.3/manual/Settings.html#background-behavior
setting Editor Mode : Play Mode Input Behavior to All Device Input Always Goes to Game View (or Pointers & Keyboards Respect Game Focus) should do what I want in the Editor, but neither works.
I also have Background Behavior set to Ignore Focus



Application.runInBackground is set to true.



The Custom HID InputDevice has canRunInBackground set to true


Any body have any ideas what else I can try?

 

Anybody?
Can a Unity person at least confirm if Background Behavior is set correctly or if I've misunderstood the documentation?