Why is this an issue?

A wildcard case statement is missing coverage of one or more possible inputs and has no default case to handle them.

How to fix it

Code examples

Noncompliant code example

module fly;
  logic [2:0] a;
  initial casez (a)
    3'b00?:;
    3'b1??:;
  endcase
endmodule

Compliant solution

module fly;
  logic [2:0] a;
  initial casez (a)
    3'b00?:;
    3'b1??:;
    default:;
  endcase
endmodule