Hi,
I’ve noticed, that after setting a field to construct, but halting it’s construction, the farmers are already allocated in the workers pool and stay farmers, even though their field is not yet constructed, and might stay like that until the construction is resumed and finished.
Not a bug, but an extremely useful feature. When putting down trios of Fields, I keep only one active at a time so all the workers work on that one, letting me start maintenance and plant the first year of the crop rotation on the nearest one.