automove on conveyor belts

My character seems really to struggle moving against conveyor belts when autoacting.

When moving manually the "wrong way" along the conveyor belts in the Crematory, I find I make a little more than 1 square progress every 2 turns (with MS=108). But while autoexploring, the game was displaying at least 4 or 5 "You pass by a conveyor belt" messages per square of progress. I'd have thought the ratio ought to be the same?