It does look like a camera clipping issue. I modified the display pipeline Draw3dText function to draw some extra elements to see what is happening so it looks like
public void Draw3dText(Text3d text, System.Drawing.Color color)
{
Draw3dText(text.Text, color, text.TextPlane, text.Height, text.FontFace, text.Bold, text.Italic, text.HorizontalAlignment, text.VerticalAlignment);
DrawLine(Point3d.Origin, text.TextPlane.Origin, System.Drawing.Color.Azure);
DrawPoint(text.TextPlane.Origin, PointStyle.Circle, 4, System.Drawing.Color.Red);
DrawBox(text.BoundingBox, System.Drawing.Color.Purple);
}
You can see in the attached gif that the geometry is being clipped at certain camera angles.
I don’t have a recommendation yet as I’m still not sure why this worked in V5 and now doesn’t work in V6. Still investigating…