Any switch, when used enough..... will break. In this case a Air Bleed Crossfeed switch would operate in the crossfeed mode "only" if was held in.
The "tit" for switch activation was broken off. Annunciation of valve position was not affected, but there is no alternate way of opening either the bleed crossfeed or the fuel crossfeed. Both are grounding items.
The switch comes as an assembly and it must be replaced as a complete unit.
A300-600 Illuminated Pushbuttons
Electrical Standard Practices Manual 20-45-11-0