Error in modeling crack propagation in a ceramic using zero thickness 3D cohesive elements.

Hello all,

I am modeling crack propagation in a ceramic using zero thickness 3D
cohesive elements. The thickness in z direction is 0.000156 mm. The
cohesive part can be seen here https://ibb.co/RNWrRGq  .

However, when I am running this model, I am getting the following error.

***ERROR: THE COH3D8 ELEMENT 1 INSTANCE BOUNDARY-1 HAS DEGENERATE VERTICES.
           THIS IS NOT ALLOWED
 ***NOTE: DUE TO AN INPUT ERROR THE ANALYSIS PRE-PROCESSOR HAS BEEN UNABLE
TO
          INTERPRET SOME DATA.  SUBSEQUENT ERRORS MAY BE CAUSED BY THIS
OMISSION

 ***ERROR: THE COH3D8 ELEMENT 2 INSTANCE BOUNDARY-1 HAS DEGENERATE
VERTICES.
           THIS IS NOT ALLOWED

I don't understand why I am getting this error? Any help will be most
helpful.

Thanks.