Hi Fernando,
Thanks a lot for your answer. Actually the part of my model that has the problem with singularity is a parallel RL circuit, the input is current and the output is voltage. For the input a standard validation signal is used for test of batteries. I tried to check the signals in every step, but the problem is still unclear to me. Actually it is highly dependent on the value of inductor. As it gets larger to 100 times larger in order of magnitude the model works fine. But in my actual model the inductor is in the order of 2e-8 (H). Taht is really weird for me. I have attached the file, can you please kindly have a look at it.