Ok. It’s hard to tell without seeing the whole thing. And I don’t want to see the whole thing 
I’d try ( for now ) simplifying this whole area. Make the tessellation just a constant ( maybe 5 ) and use single channel from a texture as the displacement.
If you don’t see the problem, then it’s something else you’re doing in the material.
( I’m assuming you’ve got ‘crack free’ on? )