Oh, and to answer your EDIT1, question, its behavior is to queue move orders to a large-ish list of random planets. When it reaches the final planet on its list of queued orders, it then becomes idle. It then waits a bit of time to generate its next list of random planets to visit.
The problem is that when it idles, it then switches to the default behavior for "enemy to AI and Human" minor factions, seek out targets on the current planet to attack (sort of like FRD). Thus, for the decent amount of time it waits to generate that new list, it chases around units on the planet it stopped at, and woe to you if it chose one of your planets.
