Hello,
the 2 O-rings have differents diameters:
The smallest one goes into the throat.
The larger one goes after the ring, if you put the O-ring in the groove (before the ring) there will be a leak at the contactor lamp switch because the O-ring seal is not suitable for the groove (the internal diameter is too large).
I still do not understand why there is this groove ? maybe what is used on another shuttle valve ?