Microbe Musher deliver too much dirt and water

They are delivering the available materials the musher needs, if you set it to 6 bars at a time they would deliver WAY less material, as a side note, it is possible to never make mush bars in a standard game

Interesting, thanks. That makes sense of it then. But (Occupational Update aside) I would be keen to see the dupes tone down the amount they pre-load into the musher when it's placed on continuous production. It would be good if they could deliver "just in time" rather than "just in case"!