Thanks for this post and explanation. I was running into the same situation recently. Although there are plenty of mouths to feed, I find those villagers just going off doing their own thing. It's frustrating!! So I too have taken to being a slavedriver, dragging them away from their laundry if necessary, and put them back where they belong.
I do have one oddity. I have 15 villagers, most of them working at research or harvesting. But then I encountered an island event -- another shipwreck to clean up. So I used the opportunity to train builders. Then one of them went ahead and started building a new hut, got 2% done and then walked away. I can't get anyone to work on the thing now. I recall reading in a recent post that 15 is a magic number for the builders. Does someone have to try to get pregnant before that gets finished?
Thanks,