you can dupe weapon modifications by trying to stack the same weapon but with differant skins when you have your hotbar full with random items and have a weapon in you inventory that is the same as the one in your hotbar but with a differant skin right click to move the weapon to your hotbar and it will try to stack the weapons but cant as it is a differant skin but it will put the attachments in your inventory but not take them from the weapon and then you keep clicking until you have stacked to your desired amount then put those on the weapon then it will dupe the amount of weapon mods on the weapon and both weapons need to have attachments its similar to the ammo dupe

updating the plugin fixed it

Thanks for letting me know about the dupe and confirming fixed, I appreciate it!