what i've found is that the bis_fnc_arsenal script uses the ui list boxes to randomize the attachments so if the primary/secondary/handgun is active, the attachments on the weapon selected will be randomized but will not when any other category is selected (e.g. select uniform, vest, backpack and the attachment will not randomize or remain the same or be no attachment if the attachment is not compatible with the weapon randomly selected from the ui list box). i recommend the script either switching to each weapon's list and then randomizing the attachments or just doing it the hard way and looking at the compatibility list in the config for one (whatever is most efficient since many users are using massive mod lists anymore).