I cleared out the map, and the convoy is huddle right on the edge of the pickup point, with only 2 of the cars in the zone.

They refuse to move for the past 20 turns, passing instantly. Guess my playthrough is fucked, since I can't even force-attack them?

The game does crate saves even if you do not, so you may just have to redo (or not redo) this single mission.