I am simulating the compression of a rubber block using Abaqus Explicit and with "Enhanced Hourglass Control" enabled. I had randomly used a mass density = 1e-9 (in the material properties) to begin with. This was able to complete the simulation.

However, I later did some literature study and changed the mass density to 1e-5, which is more representative of the real-life value of the material. Everything else was kept the same, but for some reason, after a certain time step, an element would show excessive distortion. It onsets all of a sudden (and not gradually). I was wondering what about increasing the density might cause excess distortion (if anything, shouldn't a denser material deform less, intuitively)?

The loading is slow with a smooth step function, and ALLKE<

The last 3 steps before it terminates are shown below: