So I've noticed something about SC and I couldn't find info on the quirks and info page. Basically, for unknowns reasons, transferring a unit from a allied computer player to enemy computer player makes the given units "passive". They are now enemy, and can be fired on, but don't fire back. What causes this, I'm not actually sure, because sometimes they fire back and sometimes they don't.

Anyone know anything about this behaviour??

I think it's a bug with orders. Giving units has a tendency to get the unit "stuck" to where it can't move at all. I believe you should be able to move the unit and it will fix the issue.