Are the plants going bad? Really low quality soil may make the farmer return to replant the crop.
I’m not sure if its implemented right but you should be able to increase soil quality by setting fields to fallow for a while.
if above is true it is still a bug as the farmer is still stuck doing useless work. Perhaps the farmers should leave the failed crop(for players to notice and change to fallow) or clear the tile to fallow and not plant onto poorest quality soil tiles.
Not sure what the “goes to run off to do other stuff” is really. Like what other stuff are they going to do? Mine just carries food off to storage then comes back and plants seeds. They did make some farmer changes that were not mentioned. Like multiple farmer interactions. Before when I had 3 farmers they’d get in each others way trying to do the same job. Now all 3 go off doing their own thing which increases overall efficiency.