i had this problem before, traced it back to Ai spawning with 0 as skill level, check your mission think its 1,2 or 3
eg
[[(_coords select 0) - 20, (_coords select 1) - 15,0],2,1,"DZMSUnitsMinor"] call DZMSAISpawn;
the "1"" is skill level make sure it isnt "0"