problem with reduced quadratic elements (C3D20R) while used in a node to surface contact discretization

Hello,

Can anyone explain to me what is the problem with reduced quadratic elements (C3D20R) while used in a node to surface contact discretization?

I am using a traction-seperation formulation cohesive surface and for that I can only define node to surface contact. In this case element types of C3D8I and C3D20 work but C3D20R does not work! (I am using Abaqus)

Thanks a lot,