[Sailor Steve]

It sounds like we need to make a distinction. What the convoys do when spotted isn't zig-zagging, it's weaving, and that's something they didn't do.

After a sub has been detected the convoy would either a) change course away from the sighting, b) break up and run in different directions, to regroup later, or c) continue on course, since it takes time to reload torpedoes and it's already too late for any victims.

Zig-zagging is changing course along a baseline every every few hours. The whole convoy changes course in an attempt to be where submarines can't without surfacing. Very occassionally this will steer them right into the path of the waiting submarine. The biggest SH3 supermods have had their random layers changed to do this. I don't know about RSRD.