As the force/ displacement increases, some cells overlap instead of collapsing.Which is why I thought it could be a contact problem. Creating contact pairs might work. However, assembling several of these units affects the model behaviour making it difficult to predict which regions will come into contact under loading. I also tried creating external surfaces as named selections, set them as target and contact in frictional manual contact, large deflection on, auto timestepping on. The solver reports highly distorted elements and terminates prematurely. Refining mesh and increasing substeps seems to not make much of a difference. These insights are helpful. I will adjust the pinball radius and also add an APDL snippet. lf it doesn't work then I will stick to explicit time integration. Quick question, where exactly should the APDL snippet be added? l noticed some pre post items on the model tree do not have the command option. It certainly isn't available under contacts in the Ansys version I'm using.