Initial contact between two solids

[SaeidII]

Hi, using nastran explicit analysis (sol700) I have noticed if two solids are too close to each other or touching each other; contact stress will be produced on faces of those solids and propagate into model. Since contact thickness offset of solids is zero by default and initial penetration shall be eliminated I am wondering where those stresses come from and how one can prevent this?
I'd appreciate any guide.
thanks.

 

[SaeidII]

Attached image describes the problem better:

 

[SaeidII]

Update: adding param,dyconignore*,2 to the bulk file dramatically reduced these stresses;
Default value of dyconignore is zero which means initial penetration elimination is enable; But why does it make anything worse?!