NBT data for all items within backpacks gets lost upon upgrading server version

[Aethylea]

Information

Environment information
Plugin + server version info:

Before upgrading server versions:

##### Start Minepacks version info #####
Minepacks: 2.4.31.3-T20240619115850
Server: 4077-Spigot-e9ec548-dfaa89b (MC: 1.20.4)
Java: 22
##### End Minepacks version info #####

After upgrading server versions:

##### Start Minepacks version info #####
Minepacks: 2.4.31.3-T20240619115850
Server: 4242-Spigot-0a642bd-515fe49 (MC: 1.21)
Java: 22
##### End Minepacks version info #####

Online mode: yes

BungeeCord: no

Server/crash log

Nothing weird showing up in logs - seems to load normally.

[18:28:49] [Server thread/INFO]: [Minepacks] Enabling Minepacks v2.4.31.3-T20240619115850
[18:28:49] [Server thread/INFO]: [Minepacks] Starting Minepacks in standalone mode!
[18:28:49] [Server thread/INFO]: [Minepacks] Config file successfully loaded.
[18:28:49] [Server thread/INFO]: [Minepacks] Language file successfully loaded. Language: english  Author: GeorgH93
[18:28:49] [Server thread/INFO]: Minepacks-Connection-Pool - Starting...
[18:28:49] [Server thread/INFO]: Minepacks-Connection-Pool - Start completed.
[18:28:50] [Server thread/INFO]: [Minepacks] Item name language file successfully loaded. Language: english  Author: GeorgH93
[18:28:50] [Server thread/INFO]: [Minepacks] Loading item translations ...
[18:28:50] [Server thread/INFO]: [Minepacks] Finished loading item translations for 826 items.
[18:28:50] [Server thread/INFO]: [Minepacks]  Minepacks has been enabled!  :)

Plugin config (optional)

Config is largely (maybe entirely) unchanged from its default values.

https://gist.github.com/Askylis/a9f96578110e051bad4bf710c6b708ab

Details

Description
When upgrading Spigot server beyond 1.20.4, all NBT data for all items within all backpacks gets lost.

Steps to reproduce
Upgrade Spigot server with Minepacks installed on it to any version beyond 1.20.4.

Expected behavior
Items within backpacks retain their NBT data.

Other information (e.g. detailed explanation, related issues, suggestions how to fix, links for us to have context, screenshots, etc.)
Server initially was on 1.20.4. Upon trying to upgrade to 1.21, all NBT data gets lost. This happens no matter how the upgrade is attempted. I've jumped from 1.20.4 to 1.21. I've gone from 1.20.4 to 1.20.5 to 1.20.6 to 1.21. I've gone from 1.20.4 to 1.20.6 to 1.21. I've allowed Minepacks to automatically update alongside the server, as well as manually updating it alongside server upgrades. To ensure that other plugins weren't interacting with backpack items strangely, all other plugins were removed from the server except for Minepacks. No matter how the upgrade was attempted, all NBT data gets lost. This means that all items that are stacked get reduced to a single item, durability data is lost, and all enchanted/named items lose their enchantment and name data. Attached are 2 images - "Minepacks before.png" shows how my backpack normally looks before upgrading the server. "Minepacks after.png" shows the same backpack with all NBT data now removed after upgrading server versions.

[Zoriot]

Same issue for me. Same isses when just upgrading to Paper 1.20.6
Minepacks Version is also the Same.
Would be Great if there is a workaround

[planethouki]

Same issue for me.

[GeorgH93]

Can someone affected by this issue please try this build.
It should resolve the issue for backpacks that have not yet been opened on the new version. Ones that have already been opened will need to be restored from a backup first.

[planethouki]

Works fine. Problem resolved.
Server: 4245-Spigot-0a642bd-aac911d (MC: 1.21)
Java: 21.0.3
Minepacks-2.4.31.4-SNAPSHOT-Release.jar

[Aethylea]

Works fine for me as well using the linked build on 1.21! Thank you!

[daniel-skopek]

I think the issue still persists after chaning server.jar from UniverseSpigot to Pufferfish