Building pieces which are placed intersecting large rock formations are sometimes impossible to delete, this is because the hitbox for the rocks does not line up with what is visible, causing a piece that is visibly outside the rock to be considered inside as within the hitbox.
Another problem relating to rock formations is you can place pieces that are below the terrain by using drag building and dragging underneath the terrain, these pieces can usually be fixed by digging the terrain, however in a large radius around rock formations digging is not possible. These are not as much of an issue because they arent visible but can still be snapped to by other pieces making it harder to snap to pieces above ground.
A possible solution would be to make it so you are able to delete pieces through terrain or objects with it being a toggle in the building options.
#Building pieces in certain places impossible to delete
tame oyster
junior narwhal
Hello!
Thank you for your report, we will look into such issues in our building mode iteration process :)