Seems ok BUT - as said - the projection of the map is very small, which usually solves (making the issue so small you cannot see it).
Can you make a last try ?
Get your second picture above - the one with the box near the beach - and just change the projection size of the displacement texture to, say, 10x or 20x that size.
So if now it's 100m x 100m, make it 2km x 2km, and raise displacement height accordingly.
Let's see if something happens

thanks
Paolo