I remember having an issue with the gatherer trait and harvesting...it must have been when SN came out. I stopped using the trait and that specific sim didn't have issues anymore and I haven't used the trait since.
I did come across a new (to me) issue, though. In a new game with an old sim imported in, my sim started getting that issue where plants would show the state as "Harvest", but there was nothing to harvest and the plant would never actually grow to a harvest state. Planting all new plants had worked for me before so, I tried a few things (disposing old plants/planting new, moving plants in build/buy, moving them to planters inside) and nothing seemed to work.
I read something about using sunlight as fertilizer being the problem, so I got rid of the gardening station. I planted all new plants and created a little tractor path section and everything was working again!
To test again, I added a gardening station over some of the plants and fertilized them with the sunlight and they all turned up with the same issue. Reaching maturity but never showing veggies/fruits when the plant would say 'Harvest' but would not show the option to Harvest. Everything BUT the money trees were affected