Equip item in item with inventory

Hi, i'm trying to make that so when i right click an item it automatically equips in the 8th slot item with inventory (in my case it's a bag with 9 slots). I made the procedure and it works, but when i open the bag to see if the item is equipped just isn't in there, it vanishes basically.
This is the procedure i made, i also tested it with a Shulker Box to see if my item was bugged but it still disappeared anyways. Hope someone can help with this, cheers

Procedure image: https://imgur.com/a/tHu7Z7E