Editor V10.010.010
Sorry for the unclear title (as it's hard to briefly describe it), but this report hopefully will be clearer. Feel free to change the title.
Open the editor, select any graphic set. Then place any number of terrain/objects in the level.
Select all pieces by pressing the 'A' hotkey or dragging over the editor to select all pieces.
Afterwards, if you want to change terrain pieces only, go to the terrain menu and choose any terrain.
Intended behavior: only the terrain, not the objects, should be changed. The vice versa must also be true.
Unintended behavior: Everything, including objects changes.
The vice versa can also happen when intending to change the objects only.
See GIF picture below. Only the blocks should turn blue; however, the trapdoor/exit also changes to water when they shouldn't.
(http://i.imgur.com/XZ5xC7V.gif)
Will look into it.
Took long enough, but this one is finally fixed for the next update.