When the host of a mobile defense mission decides to be a little pathetic coward & run away causing host migration while everyone is defending a point, the mission breaks. Enemies stop spawning or at least 99% do, the timer & health of your defense point goes away, & your datamass is eaten. Because the time stops, any enemies that remain don't bother to come & fight you since you are no longer at a point of interest. The only way to "finish" the mission at this point is to either