I've had multiple occasions where I am trying to build on grass floors with large areas and getting location obstructed. I am in a Multiplayer world but was hosting, tried quitting and coming back in multiple times but ended up having to completely move the grass to a slightly different area and then it worked. This has happened in a few different areas in a few different scenarios for me so I'm guessing it's something wrong with the mechanics?

I've had issues as well, I can place walls and such in a new place but not able to add things to my existing base. I can even destroy a wall but it won't let me build the same thing in it's place. I have a large "paved" space outside my house using pebble foundations with no lights or chests nearby and can't build a wall on it (of any variation).

¡No puedo cambiar nada de lugar o colocar cosas en mi base! Cualquier cosa nueva que quiera poner o cosa antigua que quiera mover de lugar me dice que el lugar está obstruido aunque está vacío, ayuda como puedo arreglar eso?

I am getting the same issue. Items that can be freely placed rather than snapped are often getting this bug.