Summary: Hearthlings while building a house seem to be getting stuck in 3 block from the ground window holes. I have built around 9 buildings and 2 have died from starvation because they will not come down.
Steps to reproduce:
Version Number and Mods in use: Dev 2881. No mods
Welcome to the forum, @Marcus_Davis 
If you have hearthlings stuck in a window, try building a ladder, it should allow them to descend to the ground.
There has been some discussions about this kind of issue, and suggestions about ways of improving it, like popping a notification saying that you have some stuck hearthling starving somewhere, or that the other hearthlings realize that someone’s stuck and go build a ladder automatically to free them.
We’ll see what the team comes up to solve this, eventually.