Simple trigger problem?

I have a simple trigger to create about 40 guys and have them walk to a certain location. THe problem is that only half move. Why would this happen? The trigger I am using to move them is: Issue order to unit owned by player 12 in RegSel move to Reg Move. Why is this happening???

Edit:
Events: every 3 sec
Conditions: Attacklevel(i) equal to false
Actions: Unit Group - Order (Units in RegSel owned by Player12(Brown)) to Move to (center of regmove))

RegSel and regmov is a region variable set earlier

Half the units move but not the other half

please post the whole thing here... the events, conditions and actions..