I am working on a model involving an SPH part that lies within a shell casing. The whole thing is being crushed by a rigid plate so there are large deformations. Once I add a contact definition between the SPH and the shell, the SPH becomes unstable as soon as the shell starts to deform. I am currently using AUTOMATIC_NODES_TO_SURFACE for the contact interface. I have tried lowering the TSSFAC in CONTROL_TIMESTEP with no success and I have tried using different SPH formulations with no success. Does anyone know of other possible causes for instabilities when dealing with SPH parts and contacts? Any help would be much appreciated.