Thanks for taking the time to open a bug report!

Describe the bug
Hi so when you get the item from your inv that is not supposed to be dropable it can be placed in an item frame and removed to get the item .

To Reproduce
Steps to reproduce the behavior:
1 get the un-dropable item and place it in the item frame

Expected behavior
Make it not possible to put non-dropable items in item-frame pls

Please complete the following information:
Version 5.2.0
Server version Bukket 1.16.5

Hi, I sincerely apologize for not responding to your Github post, I have been quite busy with some personal issues.

To prevent the "storage" of the ItemJoin item you need to add the item-store itemflag to your items.

Example;
itemflags: inventory-modify, item-store

EDIT: Marking this question as answered due to inactivity. If this did not resolve your problem, feel free to re-open this issue.