The generator matrix

 1  0  0  0  1  1  1  1  1  1  1  1 (a+1)X  1 (a+1)X  1  1  1
 0  1  0  0  0  X  X (a+1)X+1  1 (a+1)X+a a+1 (a+1)X+a+1  1 X+a+1  1 X+1 aX+1  X
 0  0  1  0  1 (a+1)X+a (a+1)X+a+1  0 a+1  a X+1 a+1 X+1 aX  1 aX (a+1)X+a+1 aX
 0  0  0  1 a+1  a  1  a  0 a+1 (a+1)X X+a+1 aX+a (a+1)X+a X+1 aX+1 X+a  X
 0  0  0  0  X  0 aX (a+1)X  X aX (a+1)X aX aX aX (a+1)X  X  0 aX

generates a code of length 18 over F4[X,sigma]/(X^2) who´s minimum homogenous weight is 40.

Homogenous weight enumerator: w(x)=1x^0+216x^40+336x^41+192x^42+1056x^43+2196x^44+2280x^45+1812x^46+5376x^47+8649x^48+10944x^49+6960x^50+19008x^51+24393x^52+28464x^53+17016x^54+33792x^55+32328x^56+28464x^57+10608x^58+14496x^59+9894x^60+3240x^61+276x^62+96x^64+45x^68+6x^72

The gray image is a linear code over GF(4) with n=72, k=9 and d=40.
This code was found by Heurico 1.16 in 38.8 seconds.