I've recently upgraded my AC25 file to AC26, did a bunch of work on it, and only now realized that the intersection priority for all my walls and meshes is broken in section. The mesh always hides the wall and foundation cut fills, leaving only the outlines, regardless of the strength setting of the material.
I've tried resolving it by fiddling with the intersection priority of both elements, moving elements forward and backward, creating new elements, but nothing works.
Starting a new project using a template created from this same file does however produce the expected behavior. No problems.
The only work-around I found is to use solid element operations on the elements, but this produces poor quality line thicknesses and is quite cumbersome to do, and will need to be redone anytime I split or duplicate the mesh.