This paper investigates the mechanical performance of soft lattice metamaterials with beam-like periodic structures, focusing on the impact of the geometric defects arising from manufacturing processes on their nonlinear buckling response. The lattice structures are modeled as assembly of shear-deformable beams under nonlinear geometric assumptions. First, eigenvalue buckling analysis is performed on the perfect lattice; then, the evaluated buckling modes are used to generate the imperfect lattice configuration through a procedure that accounts for the randomness of the imperfections. Parametric analyses are conducted to assess the influence of the main factors, such as boundary conditions, factors, maximum imperfection size, and the selected buckling modes on the behavior of imperfect structures.