I've been uneasy about what you posted, so last night I looked in the Jobo manual and instruction sheets for more information. (I have yet to find a single instance where Jobo's manual is incorrect, though I am sure than one can use these machines in ways other than what Jobo envisioned.) In Jobo's instruction sheets for the Expert drums, it specifically says that the bidirectional switch should be turned on for normal use. I fail to see how the Expert drums would work differently than the smaller drums in terms of liquid flow. I think the idea behind the bidirectional rigmarole is to avoid streaks cause by unidirectional flow, similar to the need to slosh chemicals in different directions when tray processing. Also, the drums are made to use one liter or less; if someone uses more than a liter of liquid, they are asking for trouble. That is why, when using XTol for example, you need to limit how much you dilute a stock solution. If you dilute XTol more than 1*1, you risk not having enough actual developer within the one liter maximum. At the same time, there is a definite problem with the small motors in Jobo's processors. The company obviously was not able to fully retrofit the processors for the long-term power demands of Expert drums. Since the processors work terrifically well otherwise, we are all left with doing whatever we can to keep them operational.