So I think I have found out what is up with the vanishing crabs. Those pesky land and water critters that are there waiting to be scanned but when you go to find them, they are no longer there.
Their issue ties in with the current water issue where water is being rendered above the planets horizon line.
Since these crabs walk around both on the sea floor and on the shore, they are confused by this water line issue.
Here you can see a crab performing a miracle and walking on water.
He would make it only so far and then sink to the sea floor.
Each time he popped back up to the surface, he would walk a little farther then sink again and continue his journey. So each time he popped up, he was a little further out to sea. Now you see him, now you don’t.