Question

Does applying the Corotational 2nd order terms in the CLPOP2 help with convergence in the model when the elements have suffered plasticity? 

Answer

These terms help with large deformation due to elastic or elastoplastic buckling of the frame elements. If you have a large deformation, that may help. If the convergence issue is caused by joint failure and elastoplasticity of the member, adding these terms doesn't hurt either, but they may slow down the analysis.