Staad Stress plot

Furthermore there appears to be an error in Staad with respect to the sectional member stress plots. In many instances the plot 4 corner stress points do not match my Mathcad results. Of course this could be considered a failure on my programs ability to calculate the correct stresses, however. Upon further investigation, it would seem Staad Pro is using incorrect forces at the section for the stress calculations. What I have found is; if I print out the section forces and stresses using the Staad file list output, they are exactly the same as my program and give the exact 4 point stresses when combined. If I select the 4 points directly on the stress plot and list them on the Profile Stress Plot tab, what I have found is that the listed forces attributable to the calculated stresses are not correct and are for different sections than that selected (both MX and MY appear to be at different locations). The plot output also appears to be different to the forces shown when double clicking on the member in question and selecting the Shear Bending tab and inputting the section at which forces are required, making sure the correct load comb is selected at the section in question.

1, Has anyone noticed/experienced this issue ?.
2. Does anyone have an explanation apart from the Staad program using incorrect section forces ?

I also include a pdf which clearly shows what I am referring to.

Any comments would be well appreciated.