Okay, thanks to Dependencywalker (Really a useful program when something errors!) I was able to figure out the cause.
Whenever you think you have all vcredist installe...

Have you made sure to update your gdbdb after putting it in your map? If you have and it's still failing I've noticed this with some materials I've ported when I've failed to port them across.<...

Need to add player quote in harrybo21_give_gun() function. In _zombiemode_weapons.gsc its done via this:

self maps\_zombiemode_audio::create_and_play_dialog( "weapon_pickup", type );

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