Corner vs central stresses in design of plated elements

Good day to all,

I am designing plated element (Walls and Slabs). I have faced an issue when considering the maximum stresses of an element. In my model Corner stresses are always higher than the central stresses for an element. the question is, which stresses should be used in designing for flexural and shear? if the answer is; the central stresses should be used then why the corner stresses are automatically selected when designing those elements using CONCRETE DESIGNER? some friends of mine are using the central stresses for their design, is that considered critical and/or faulty design? 

I hope I can get answers to my questions

Attached are some samples

Corner Stresses

Central stresses 

Bending stresses from CONCRETE DESIGNER

Regards