It is not a flaw but a property of the material. The surface is made of genuine carbon fibres, and the diamond pattern arises from the way they are woven. In the process the individual diamonds inevitably come out less than perfectly uniform; small gaps in the pattern, edges very slightly out of line and differences in sheen are part of it, and are found on the factory's own photographs and on display pieces too.
A perfectly regular diamond pattern is, on the contrary, an indication that no genuine fibres were used at all, merely a carbon look of the kind common on instrument panels and trim in the motor industry. Working genuine carbon fibre is so demanding that it is otherwise undertaken chiefly where there are technical requirements behind it, in motorsport, for instance, and in aircraft and shipbuilding. A slightly irregular pattern therefore speaks for the pen's authenticity and is no ground for complaint.