Ok So I have seen this for awhile, floating river mouth tiles. In Cartographer I have been working to figure out the magic formula for ensuring that a river mouth on a stamp doesn't end up landlocked and floating over the terrain, I am about to give up, even telling the tile to be on the coast (which is not optimal) or in the water doesn't ensure you won't get a floating river mouth when the stamp is placed with random map generation.

I have also tried ensuring I select water tiles all around the river mouth when i save the stamp, problem still happens. Can we get the magic formula to make sure this doesn't happen I don't want to make a whole ton of stamps with this problem plaguing me at every turn.