Liaison's should not be provided IMHO from this reading of the rules.
In MHQ a liaison unit appears. Once started in MM the liaison unit disappears. Recommend adding a button to the "Deployment Frame" that would randomly select an undamaged/uninjured unit from the "Deployed" units (Unassigned doesn't count).
I traced through the generation of SLCache2 missions several times and could not reproduce the problem. Moreover, I see no way that the situation described here could have occurred. If you remember anything else about the incident, I'll take another look. Otherwise I don't see anything to fix.