Our group has established a RSM connection to solve system coupling (Transient Structural & Fluent) problems. However we discovered that the RSM/Cluster does not provide constant results. We have tested a small project many times. Results of the same project ended up differently. Only a few run succeed and finished as we expected and the running time was around 8-12 hours. However other tries ended up either ran into connecting/license problem or were continuously running until they reached kill off time (120 hours), which we could not understand. Such issue was not found if we ran these two modulus individually. Can somebody help us figure out why our RSM solver behaved like this?