Not sure if this is a bug or not. The jungle grass and broken grass flooring wouldn't set to build under the stone wall corner pillars and stone wall segments. Had to do some fine tuning scooting things away from the property line (wall location) last night to get the grass set to build.
Dracaena
I have been able to place both under buildings, so I'm not sure. Is it possible that the footprint for the stone flooring itself was actually in the same place as the footprint for the pillar?