Cletus - Problem

I had a similar issue when it came to placing the Gazebo and I just had to keep doing it over and over, eventually it just worked. Perhaps there is a way to reset your character, like putting him in the farm then putting the farm in your inventory, or making him dig through the trash and storing the dumpster. Then re-attempt to make him complete his task. Sometimes quests just get stuck, but they do eventually work again. Hope it fixes for you soon!