I can't open your file as you're using the Educational version; but from your last screenshot, it looks like the problem is with the 'edge' surface, not the top one.
Because this surfaces touches itself at various points (and with an acute angle), it's possible that these points are where the mesh falls over. You might need to model it with small gaps instead of touching, and then use either contact interfaces or rigid links (or something else?) to connect the places where the waves touch.
I'm just guessing though...
