We were having the same issue on our server with trucks going to sales points. Went from modded truck/trailer to base game ones and have no issue. We believe there is some conflicts between some modded vehicles and Autodrive. Server would lag pretty bad when modded trucks were hauling on autodrive, but if they were driven by the player would have no lag issues. Little lag stutters would happen in sync with modded truck flashers while on autodrive. No issues with base game trucks.