I have two saves where one to three workers will idle - they’ll wander around like they have nothing to do (rather than behaving as though they’re physically stuck) but they won’t path anywhere - they won’t eat and they’ll sleep on the ground instead of beds. There’s plenty of jobs ready for them to do, such as building, harvesting, and stockpiling.
This can be reproduced by loading during an active game. Loading the game for the first time after starting up will result in expected behavior, but subsequent loads will result in a few workers in particular to idle (always at least one, most of the time it’s Elena, but the trapper and more uncommonly the carpenter are candidates).
This is using an AMD Phenom II x6 1075T and an Nvidia GTX 770 (2 gigs VRAM) on Windows 10 Technical Preview. 6 gigs of RAM.