Shear wall design

Good Day fellow colleagues,

I have tested two models to complete a shear wall design using staad pro. In one model I included only the shear walls, beams and columns and in the other model I included all of the above mentions elements plus the slab (modeled using plate meshing). After analyzing the designs i observed that the model without the slab failed one of the shear wall designs due to a out-of-plan moment (My) that was too large, while all the shear walls in the model with the plates were designed without any failures. Why did this difference occur between these two models. The only other difference in the models is the gravity loading, in that the model with the beams only uses the floor loads command , while in the model with the plates I replaced those loads with plate loads. 

I have also included screen shots for the specific portion that failed from both models.

FAILED WALL MODEL

PASSED WALL MODEL