If a converged solution from springback prediction cannot be obtained after trying many different combinations of parameters, what else can I do?

Use dynamic relaxation method. Usually this is not necessary. For most of the application jobs, converged solutions can be obtained if the jobs are set up properly.

If the part is very flexible, it is possible that convergence is difficult to get with implicit method. However, dynamic relaxation method is time-consuming, and it is should be used only when explicit method fails.