When the constant nail slip deflection for gypsum wallboard (GWB) is so much greater than the deflection for the wood side that it draws no load, the program was still assigning the constant nail slip deflection to GWB. As a result, the deflection of the shearline was much greater than it should be, and it’s stiffness is much less, causing it to draw less loading under rigid diaphragm distribution or when loads are distributed to dissimilar materials along a shearline. This happened most often under low loading conditions, and has been corrected.