Why is this an issue?

All case items should be different. Having identical case items is likely due to a bad copy/paste and will likely lead to functional issues.

How to fix it

Code examples

Noncompliant code example

unique casez (select)
  3'b000: operand = accum0 >> 0;
  3'b001: operand = accum0 >> 1;
  3'b010: operand = accum1 >> 0;
  3'b000: operand = accum1 >> 1; // Noncompliant: 3'b010 case already defined above (first case item)
  3'b1??: operand = regfile[select[1:0]];
endcase

Compliant solution

unique casez (select)
  3'b000: operand = accum0 >> 0;
  3'b001: operand = accum0 >> 1;
  3'b010: operand = accum1 >> 0;
  3'b011: operand = accum1 >> 1;
  3'b1??: operand = regfile[select[1:0]];
endcase