I've just recently playing around with Sandbox mode in @Gwido's save file.
I tried to spawn water with Brush tool, then used Pipette to clone water properties (not shown in the video) and I don't do anything else to it.
Then I tried to check the place where I deconstructed a Sink when I was discussing some things about ONI with @Gwido personally.
Then I found I can no longer build Sink in the exact same location.
But the remaining Sinks above and in the other rooms are okay.
Only this exact spot is bugged.
Try to build Sink via the save game. I'm sure it'll remain the same over there.