I *think* I have encountered a bug. I'm at the pyramid, I've used one Cog Wheel to activate a ladder on the right side, then used two smaller cog wheels on the second ladder on the left side. Now I cannot use the second Cog Wheel to activate the ladder on the left side.
Here's a fairly small solution to teachers.
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 "Submachine 10: the Exit"){kind=icon}
 "Manufactoria"){kind=icon}