duplication of items in addon

[Marazota]

hello i have old addon similar to inventory insight, where is scans all your item and add them in one list in separate UI. author mia long ago so i want to ask here

every time i open it i need to push re-scan button, because it duplciates each item
if i will not re-scan and open it many times again and again items will duplicate each time and list will be come bigger and bigger

here is addon itself, anyone can help, what need to be fixed there?

https://drive.usercontent.google.com...xport=download