toshtest.3dm (1.6 MB)
Rhino 6 (vanilla) latest service release.
When I edge fillet the hole (red) 0.1 rolling ball, the shaded and render modes look wrong. Geometry looks OK in wire-frame.
Actually, filleting that edge produces bad objects, to solve this, you can
Explode your object, select the bad objects by
SelBadObjects command and then
trim again to fix the problem: