Hey,
If I understandwith your original setting:
Brown = L
Blue = N and A2
grey = lamp
Black = A1
Is it true?
Is ok, you need to connect like that:
Fibaro FGD 212
exemple 1:
Brown = L
Blue = not connected
Black = Sx AND N (momentary switch)
Grey = Lamp
and you need a second wire between S1 and momentary switch
exemple 2:
Brown = L
Blue = N
Black = Sx (momentary switch)
and you need a second wire between S1 and momentary switch
For the 2 exemples, you need a second wire to connect the momentary switch.
If we can, try to get the wire between the momentary switch and the live lead (L).