Using scripts from "Pastebin" or YouTube videos often results in:

: One of the most famous scripts targeted vending machines. While basic glitches were quickly patched, a "better" script emerged that used an injector to manipulate item quantities—demonstrating items turning from 10 into 1 million in seconds .

If you encounter a bug that accidentally duplicates items, it is best to report it in the official Islands Discord server rather than trying to use a script, as the latter is much more likely to result in a ban. Islands Dupe Script Better Better