It is well known that the presence of initial penetrations can spoil the accuracy of the analysis. A few days ago, while working on ODB barrier, some strange spikes in energies was suspicious even with IGNORE turned on. To understand this, I simply did a simple shakedown and generated some 100 d3plots to capture the effects. After analyzing the results, the strange effects were attributed to the presence of initial penetrations. What is interesting is these small penetrations can introduce contact stresses in the structures and can propagate through them. Attached is a clip generated from the barrier study where the simulation was run with no external loads, body forces, and boundary conditions. You can see the source of initial penetrations and how they travel at the top of the barrier (cladding sheet).