Auto Convoy mechanism - it routs things very poorly, and then they waste time trying to go around threats.
When you first set up a (CS) convoy from say SFO to Noumea, its route is assigned to go through the Marshall/Gilbert islands, despite the fact that the IJN is in residence there. Which you correct with way points. If you just let it go the way it wants, it might detour around the air threat, but the problem is that if the IJ moves, say, a Betty group to a nearby base on day X, on day X+1 the convoy is toast. On the odd occasion where you forget to set the 'return same way' button and a TF wanders off towards Makin Island, carnage results, regardless of telling it to move the safe route.
Eventually in about 1945 you can use the auto-convoy system for backwaters, but if a convoy from origin port to destination would, left to its own devices, go within Betty/Emily/Peggy/Rita range of any functional IJ air field, it is best to use a waypointed CS convoy for that destination.
"You may find that having is not so nearly pleasing a thing as wanting. It is not logical, but it is often true."
- Cdr Spock