Attached an image showing the thing. It´s a continuous floor that curves up . I have tried both Meshsmooth and Turbosmooth bit its the same problem. as if I had different smoothing groups in the object. See image and a stripped down 2018-max-file.
Strange artifact on Geometry, Some kind of bug
Centileo for Blender
Centileo lights name in viewport
How do I do Caustics on Glass?