I just posted in Idle Hearthlings and newcomers another related issue that may have a simple fix and may help to determine the cause of the idle worker bugs.
(in this particular case, it was that my hearthlings were hungry but the door to the dining hall was blocked by scaffolding, so they just stood around hungry, and did not proceed to eat, nor do the next thing on their work list.
…new users cant post images…
— 05SEP15 edit —
After further observation, I am not sure if the door was indeed blocked by the scaffolding, as I have seen hearthlings go through the scaffolding and doors on other buildings under construction. But they definitely just stood around hungry.