[BUG] Another duplication issue

[Sixsoul]

Describe the bug Ahhh, sorry back again with another one. I've had multiple player reports now of backpacks duplicating the contents of other backpacks. Example: I have one backpack with 64 Netherite Blocks in it and another backpack with 1 Dirt Block in it. I open the dirt backpack and suddenly instead of showing the dirt that it should have, it has the Netherite Blocks in it for some reason. You can remove the blocks from both backpacks individually and boom, now you've duped your netherite blocks.

To Reproduce Steps to reproduce the behavior:

1. I am unable to recreate this issue myself, but I've now had 3 separate players report it happening all at different times. According to their reports there is no clear method to replicate the problem, it just happens randomly. I thought it was a fluke but it seems to be a recurring issue now.

If it's worth anything, I use SQL for storage.

Expected behavior Backpacks should maintain their own inventories instead of duping others.

Info (please complete the following information):

• Server version:Paper 1.18.2
• Client version: Any
• Plugin version: 1.3.16

[LoneDev6]

This is quite strange. Anyway mysql is not the issue since it doesn't sync physical backpacks, only the virtual ones opened with /ebp.

I really need your players to find out exactly how to trigger this behaviour or I cannot elaborate a fix. The plugin was heavily tested and no duplication happened, maybe it has to do with another plugin (which I have to add support obviously).

[Sixsoul]

I mean...there is no way to recreate it reliably. It's just a random occurrence. All the player does on their end is have more than one backpack and then open one and boom, it dupes the other one sometimes.

[LoneDev6]

I'll do some tests to see if I can manage to do that

[adamboof]

REDACTED

[adamboof]

This error gets posted to the console when issue occurs

java.lang.NullPointerException: Cannot invoke "org.bukkit.inventory.Inventory.getContents()" because "<local4>" is null
    at dev.lone.EpicBackpacks.d.a(SourceFile:86) ~[EpicBackpacks_1.3.16-r1.jar:?]
    at dev.lone.EpicBackpacks.d.a(SourceFile:326) ~[EpicBackpacks_1.3.16-r1.jar:?]
    at com.destroystokyo.paper.event.executor.MethodHandleEventExecutor.execute(MethodHandleEventExecutor.java:37) ~[paper-api-1.19.2-R0.1-SNAPSHOT.jar:?]
    at co.aikar.timings.TimedEventExecutor.execute(TimedEventExecutor.java:80) ~[paper-api-1.19.2-R0.1-SNAPSHOT.jar:git-Paper-196]
    at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:70) ~[paper-api-1.19.2-R0.1-SNAPSHOT.jar:?]
    at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:670) ~[paper-api-1.19.2-R0.1-SNAPSHOT.jar:?]
    at org.bukkit.craftbukkit.v1_19_R1.event.CraftEventFactory.handleInventoryCloseEvent(CraftEventFactory.java:1523) ~[paper-1.19.2.jar:git-Paper-196]
    at net.minecraft.server.network.ServerGamePacketListenerImpl.handleContainerClose(ServerGamePacketListenerImpl.java:3069) ~[?:?]
    at org.bukkit.craftbukkit.v1_19_R1.event.CraftEventFactory.callInventoryOpenEvent(CraftEventFactory.java:1337) ~[paper-1.19.2.jar:git-Paper-196]
    at org.bukkit.craftbukkit.v1_19_R1.event.CraftEventFactory.callInventoryOpenEvent(CraftEventFactory.java:1332) ~[paper-1.19.2.jar:git-Paper-196]
    at org.bukkit.craftbukkit.v1_19_R1.entity.CraftHumanEntity.openCustomInventory(CraftHumanEntity.java:354) ~[paper-1.19.2.jar:git-Paper-196]
    at org.bukkit.craftbukkit.v1_19_R1.entity.CraftHumanEntity.openInventory(CraftHumanEntity.java:339) ~[paper-1.19.2.jar:git-Paper-196]
    at dev.lone.EpicBackpacks.d.a(SourceFile:162) ~[EpicBackpacks_1.3.16-r1.jar:?]
    at org.bukkit.craftbukkit.v1_19_R1.scheduler.CraftTask.run(CraftTask.java:101) ~[paper-1.19.2.jar:git-Paper-196]
    at org.bukkit.craftbukkit.v1_19_R1.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:483) ~[paper-1.19.2.jar:git-Paper-196]
    at net.minecraft.server.MinecraftServer.tickChildren(MinecraftServer.java:1473) ~[paper-1.19.2.jar:git-Paper-196]
    at net.minecraft.server.dedicated.DedicatedServer.tickChildren(DedicatedServer.java:446) ~[paper-1.19.2.jar:git-Paper-196]
    at net.minecraft.server.MinecraftServer.tickServer(MinecraftServer.java:1397) ~[paper-1.19.2.jar:git-Paper-196]
    at net.minecraft.server.MinecraftServer.runServer(MinecraftServer.java:1173) ~[paper-1.19.2.jar:git-Paper-196]
    at net.minecraft.server.MinecraftServer.lambda$spin$0(MinecraftServer.java:305) ~[paper-1.19.2.jar:git-Paper-196]