how to solve the ZERO OR NEGATIVE VOLUME problem when using very soft material?

Hi,

I am trying a simple impact analysis like radioss example 26 ruptured plate ( I am not interested in the rupture, just want to try an impact problem). I am using a soft non linear material M36_PLAS_TAB with a stress strain curve (E=8Mpa,nu=0.42,rho=1.412e-6Mg) and fixing the whole bottom surface. I used the volume tetra mesh to mesh my disk. ( I am using solid elements instead of shells as a basis for a more complex problem I am working on)

The model was working fine with linear elastic materials...

I read a few posts about this problem. There it was suggested to use a really thin linear elastic surface on top.
And to change the element formulation.

Could you please elaborate more in detail the steps to overcome this problem?

Thanks!