As per the title.
There is presumably something going on with the pathfinding, so that in order to collect some sort-of-near item or something, it is driving on massive circuitous routes around the map, hundreds of tiles from the factory, often going directly near biter nests.
That is, some item that is nearby in straight-line distance is only accessible - due to structures like lakes and walls - via a long indirect route that goes far from the two endpoints.
