At Autodesk Revit forums I saw a post regarding disappearing curved walls. These walls were shorter than the current view range cut plane. When the Wall subcategory Non Core Layers is turned off only these curved short walls disappeared. Other walls of the same type that were straight remained visible. It looks like a bug to me.
In my testing, when the sub-category for Non Core Layers (Detail Level must be Medium or Fine) is turned off the wall will disappear
when it’s height is not at least 2 feet above the cut plane setting.
For example, I can make a wall disappear if it’s height is less than 6
feet when the cut plane (view range) is 4 feet. Enter anything 6 feet or
higher and the wall reappears. This image is some full height walls and some walls that are 4 feet tall (lighter gray walls).
This is the setting I turned off in Visibility/Graphics.
This is the result, the curved 4…