Cohesive element modelling problem in ABAQUS

Dear All,

I am modelling a 3 point bend specimen with Cohesive elements tied to the upper and lower halves of the specimen in 2d.

The problem is that the CZ elements perform properly only for a combination of element sizes, i.e. a combination of element size of structure and CZ elements, for instance in my case the structure/specimen element size is 0.2mm and CZ is 0.001 or 0.002. For any other combination the adjacent elements bend as shown in the attached image.

I will be glad if someone could explain this behaviour and the solution.

I also attach the input file.

I am not sure about the node numbering issue of Cohesive elements. I meshed the elements assigning sweep path along normal to the crack propagation direction. 

With regards,

Abhishek