Similar to what @Big_Boy mentioned, it's only occurred to me twice where they went across the world to gather resources when there are some close by and they all died of hunger or thirst. I've noticed those times they were mostly quarrymen again it happened once population reached past 25.
I've also got the same issue. The game starts off fine and once the population reaches around 25-30 nuggets, majority start to stand in one place until they died. I've noticed it more so in quarrymen or couriers. I've also noticed some nuggets wandering all the way to the other side of the world as well then dying of thirst. The image is of all the dead nuggets that have gathered.