Possibly related to the disappearance of ground units mentioned earlier, but the workaround does not aplly, since the ground units disappeared completely.
Summary:
begin situation:-1 colony on Mars, with empire population status
ground forces present: 4 Heavy Assault + HQ, 4 Engineer + HQ, 1 Garrison, 1 Replacement, all at full readiness
-1 colony on Mars, human archeological dig, formed automatically by Aurora when defeating some robotic guardians previously
no units/structures present
-1 freighter fleet (5 ships) in orbit of Mars
-1 civilian freigther in orbit of Mars
event 1: robotic guardians disturbed
event 2: player interaction: order ground forces in Mars colony to attack non-PDC(unknown race)
end situation:-1 colony on Mars, vanquished population status
no ground units. They disappeared without mention in the event log.
(second colony was deleted automatically by the program)
-6 freighter fleets (1 ship). The civilian freighter had come under player control.
link with screenshot of event log here:
viewtopic.php?f=19&t=2875