Thanks for taking the time to open a bug report!

Describe the bug
I installed Pro Death Chest. Even though I have death-drops enabled the item appears in my chest on death.

Pro Death Chest:
https://www.spigotmc.org/resources/%E2%AD%90pro%E2%AD%90-deathchest-1-8-1-16-x-no-more-losing-items-after-death.63316/

You may be able to duplicate this with another graves plugin. I only tested with Pro Death Chest.

Here's my item definition in case I set it up incorrectly.

id: NETHER_STAR
slot: 8
name: '&eHub Menu'
lore:
- '&7Hub Menu'
commands:
 - 'myhub'
itemflags: item-store, death-drops, self-drops, inventory-modify, give-next
triggers: join, respawn, world-switch
permission-node: groups.default
enabled-worlds: ALL

To Reproduce
Steps to reproduce the behavior:

1. Setup item as defined above
2. Install Pro Death Chest
3. Die

Expected behavior
I expect my ItemJoin item to not appear in the Death Chest.

Screenshots
If applicable, add screenshots to help explain your problem.

Pastebin
Even if it is not related to the problem, please include ALL configuration files in separate Pastebin.com links as well as any related error codes from the console window.

Please complete the following information:

• Resource Version and Build Number: ItemJoin-v5.1.0
• Server Version {"oldVersion":"git-Paper-446 (MC: 1.16.5)","currentVersion":"git-Paper-449 (MC: 1.16.5)"}%

Additional context
Add any other context about the problem here.

So I am currently unable to replicate this with DeathChest v3.4.13 and using the latest ItemJoin snapshot. It seems to function properly (as-in not dropping the item into the chest).

I would suggest updating and let me know if the issue continues;

Link: https://ci.craftationgaming.com/job/ItemJoin/666/
Remember to remove your old ItemJoin.jar file

See devlog for changes; https://github.com/RockinChaos/ItemJoin/wiki/DevLog

Do note; This build contains a major change to item commands so any prior commands will break until fixed.
I have removed the commands: identifier node from the items. So commands which resembled;

    commands:
      interact-right:
      - 'player: deluxemenus open navigation4'

Should now look like;

    interact-right:
    - 'player: deluxemenus open navigation4'

Do make sure you implement proper yaml formatting as when you remove the commands node there is two spaces in-front of the interact-right node you need to remove.

This bug has been officially fixed in the release of ItemJoin v5.2.0.
You can grab it here; https://www.spigotmc.org/resources/itemjoin.12661/download?version=383801

Please read the changelog as the documentation has not been updated yet;
https://github.com/RockinChaos/ItemJoin/wiki/Recent-Changes