I'm unsure if this is the right place to post my issue, but I must remove the physical backpack from the player's backpack slot to resolve it. I don't have any plugins that control the physical backpack.

this is the error I got from the console

xxx.xxx.xx.xx:xxxxxx /xxxxxxxxxx/xxxxxx disconnecting: Object reference not set to an instance of an object. at %55f82857e5ca442cd75ed2b55d0557d513576a82.%127a1f2d3f2de5d208a7fe4bcece005d7bb40b6d (%183ae511009a32ca4bb38d6a9e2181ce08695f1a %1e23de3a49351e65c991dc07e97342b28647d8bd) [0x00000] in <00000000000000000000000000000000>:0 at %7157fadb85b33623de2034a65bc857a88d3f36b3.%127a1f2d3f2de5d208a7fe4bcece005d7bb40b6d (%183ae511009a32ca4bb38d6a9e2181ce08695f1a %1e23de3a49351e65c991dc07e97342b28647d8bd, %55f82857e5ca442cd75ed2b55d0557d513576a82 %d89c26b16e613b74c83a6e990579caddc2b81b6e, System.Boolean %973972e215d024c9768d427578982c228cf181f3) [0x00000] in <00000000000000000000000000000000>:0 at %a4b473813b8048d6030fc6c1a46e0de2d2e722a4.%127a1f2d3f2de5d208a7fe4bcece005d7bb40b6d (%f6da8eaec241a2f2f35becf3c6de2f74e6ede5de %e4e30e8312be4740fe2bdee0ed88fec1e76422b2) [0x00000] in <00000000000000000000000000000000>:0 at PlayerInventory.%127a1f2d3f2de5d208a7fe4bcece005d7bb40b6d (%e72b64fbe0eb3002bb07bd6318a557735ef0648c %de4c3f398440bd422478dee04b9e6f76b02d1a06) [0x00000] in <00000000000000000000000000000000>:0 at BasePlayer.%127a1f2d3f2de5d208a7fe4bcece005d7bb40b6d (BaseNetworkable+%7e71e6b1c5ec5f4826fd5a9baac2f84395c0bf97 %8aae8f0e2e18faf114aa6973f930a7d26d28a37f) [0x00000] in <00000000000000000000000000000000>:0 at BaseNetworkable.%067e5bbe660ae3dc4f2b61c98d633b07ad48c2f5 (%ea34a45fd6eaaf836754e0a61f97fe9dd13c274a %be5c1a06890d688cdc836284ae4cdc2c8b7ecfdf) [0x00000] in <00000000000000000000000000000000>:0 at Client.%8fe0d6df4c964e4f6804d49dc6dd962f62dd484e (%ea34a45fd6eaaf836754e0a61f97fe9dd13c274a %8aae8f0e2e18faf114aa6973f930a7d26d28a37f, System.Int64 %397343d7932b6098bc325d9e7a3e518163009be7) [0x00000] in <00000000000000000000000000000000>:0 at Client.%dd361683e1adc22c299275981dbcf71f069f9968 (%a3de95091867c6e0394859316ac9faacc34690e4 %c59221ae3dbccf382f2c35e1bfbce50d665a857b) [0x00000] in <00000000000000000000000000000000>:0 at %59e938bbdd008c8a6b4535d208abe680dbddf4dd.%a565c23271a56bd4811271b15c3418f4aa81b46d (%135e19e9c67994393e829aec8d2d898eb06887d9 %8eedd4816eef8382d77bfc7088421e8b95f25e00) [0x00000] in <00000000000000000000000000000000>:0 at %1c413b615ff3c2561906c24fbfdca378134c0875.%4a50c65db12886e32858a8ae23b9e49ef600b1fb () [0x00000] in <00000000000000000000000000000000>:0 at Client.Update () [0x00000] in <00000000000000000000000000000000>:0

This plugin doesn't have any interaction with or relation to the physical backpack.

WhiteThunder

This plugin doesn't have any interaction with or relation to the physical backpack.

Thank you. Could you please explain what is happening with these errors

Unfortunately, that error is essentially obfuscated and therefore appears as garbled nonsense. It would take me hours to even devise a strategy to decipher it.

Even though you do not have any plugins which interact with the physical backpack, I would check if you have any plugins which interact with the backpack slot. For example, plugins relating to parachutes or diving tanks.

Thank you for your time, I appreciate it. I don’t believe I have any plugins for that.

I used to use the Backpack Slot Item plugin but no longer use it.

This issue started today after a server restart. I also noticed that some other plugins are having trouble with the 'OnServerInitialized'

After extensive testing to identify the root cause of the issue over 150+ plugins, I determined that it was caused by the ItemRetriever plugin.
I created the items from the CustomizableWeapons and CustomizableProtection systems, which rely on the CustomItemDefinitions by 0xF.

If I transfer any crafted items from this plugin to either the physical backpack or the backpack plugin, I get kicked from the server after about 5 seconds and am unable to rejoin because I'm instantly kicked before the wakeup screen appears.

To resolve this, I have to kill my character from the console command and clear my inventory. unload the RestoreUponDeath plugin to prevent it restore my inventory and backpack.

I see. It sounds like the incompatibility is between Item Retriever and Custom Item Definitions (CID). Glancing at the CID code, I see it uses the OnEntitySaved hook to mutate network messages before they are sent to the player, to replace fake item IDs with real item IDs, presumably to avoid kicking the player. The problem is probably that CID runs OnEntitySaved before ItemRetriever (due to alphabetical order), so when ItemRetriever also tries to mutate the same network message to add items from other containers, it adds them with the fake item IDs and CID doesn't get the opportunity to swap those out.

I have pushed a change to the plugin's GitHub repo which should skip networking any items that are flagged by the CustomItemDefinitions plugin. Please test it out and let me know if it resolves the issue.
https://github.com/WheteThunger/ItemRetriever

I can confirm this fixes the issues, thank you for your help.

I also noticed that the CID updated at the same time.