I thought about it as well. I usually delete "temp" folder several times during a day, I always pay attention to this, so the files are not corrupted.

Anyway, may a not fully triangular/tetrahedral mesh cause this strange behavior? I always try to use more quadrilateral/hexahedral mesh type to decrease the overall number of mesh elements/nodes. Other competitor softwares warn the user to use triangular mesh in case of nonlinear material but there is no such restriction in ANSYS AIM.

May it be worthwhile to use tetra mesh when using nonlinear material? Could this be the problem? What do you think?