If you are missing the Z's then it might be caused from differences between my default regional-settings (OS) and/or the used char-sets respectively collation-settings and your configurations. Maybe you could adjust them in any way.
Deducing from this it indicates that in your char-list is any additional/different char compared to my "standard" alphabet. To know it might be useful for any adjusting approaches to the settings.
An alternatively might be just to increase the number of chars by using 27 instead of 26, like: