I am not too familiar with studies that contain different materials of significantly different stiffnesses but from the sounds of the error I would think that maybe Simualtion is having a problem with the contacts between the metal and the plastic. Sorry that may not be much help.
Thanks for the replies guys.
I took a closer look at my restraints and I did see that the plastic as it was sliding against the metal was experiencing a wobbling kind of effect due to which it was loosing contact with metal. Additional restrains solved this error.
However, another error creeped up showing that the "logarithamic strain was too large" and the problem kind of hung up. Changing the material model solved this error too.
Initially I was using a Non-linear material model with a stress-strain curve. I changed it to a linear material model since the plastic was not undergoing any significant deformation and most of the deformation was on the metal.