A Worker went into infinite loop
Here is a savegame where one got stuck in my Dungeon Core, making him to blink away only to run again into it, rinse and repeat.
Game Version:
Steam Public
Platform:
Windows
So I did load your save game and saw a worker next to the core.
But he just went idling away and no issue appeared, so I loaded it again twice with same result.
So all I can guess what ever issue you had there we did fix meanwhile either in one of the recent hotfixes or internally which will be then fixed with next patch.