Multimachines working properly
Well, that took a while. There weren't too many other chunks I could break off, so I ended up tackling all the bugs one after the other. Multimachines now work, and can produce circuit boards from ingots, but I suspect that there are other bugs and a bunch of refactoring in the immediate future.
To be fair, I did spend some time tweaking things, like adding visible hopper entries to the machine so that it's more obvious where to send the stuff, and it seems to work well.
For now though, the bulk of the game mechanics are in and it's time to start thinking about how the game itself will work, and adding game data: levels, items, more machines, etc, etc. I don't want to get caught by leaving everything until the last minute and having to crunch overnight...