When more than two hearthlings are placed into one combat party, the other members will only attempt to patrol and chase the first two members of the party, they will not eat or fufil any other tasks. To reproduce this you simply have to add at least one hearthling to an existing party of two, the third will only follow the first two, lagging behind and eventually starve
I have tried to add even numbers of hearthlings in hope that it was just an odd number being the issue however this has not fixed it
Release-877 (x64)[M]