Symmetry Analysis for Solidworks Simulations

I have a problem with symmetry Restraint. My model is a half of branch conection with its respective run pipe, i did the run pipe of 8 inches and the branch of 4 inches, apply the symmetry restraint and it works, however it becomes in a whole mess when the model is larger, for example 30 inches for the run pipe and 18 inches for the branch connection

Whyyyyyyyyyyyyyyy???

SolidworksSimulation