VTOL Jet Booster on a combat VTOL disappears from Equipment tab once assigned a location

[assaultdoor]

Using MML 0.47.4 on OS X with Java SE build 1.8.0_51, when I assign a VTOL jet booster a location in the Assign Criticals tab, it vanishes from the list of equipment in the Equipment tab. It does not reappear on the list if I remove it from its assigned location.