Water disappears when I try to change landscape geometryor scale

Hi, I am new to unreal Engine, and watched loads of tutorials about landscapes and water systems. However, when I add landscape, (with edit layers selected, positioned at 000), and then I add ocean water using new water system plugin, I cant change the form of the island! When I try to make it bigger or just add spline points and change geometry, part of the ocean water weirdly disappears! Here are the images of before transforming the landscape and after trying to change the geometry by simply dragging the spline points!
Please help as I can’t find any answer of why it happens!

Did you solve this??