I made a crafter building for blacksmith and mason, they palced the mason workbench inside but not the anvil one for some time, and now I realsied I got 2 people stuck in there, after thinking about it I also noticed the floor is red when in building mode so that could be connected.
weaver was the one who placed mason workshop inside
the other dude recently joined the town.
Running 64 bit, 2176 build (unstable one)
I might add a video of it in few days