I first noticed this with my current factory set up: I have two refineries, one between the silos of unrefined resources that leads to the fabricators, and one on the loop that sends unrefined resources back to the conveyors located just after the first refinery. Every tick of the conveyor system (the time it takes to move resource chunks from one conveyor to the next) it would alternate which refinery was calling for unrefined resources, which caused excess resource chunks to clog up my factory line, as well as refineries ignoring the needed resource chunk.