https://pastebin.com/68kk826j

Server runs completely fine, but client-side crashes happen with this error. A backpack is placed in the chunk, and removing/picking it up fixes the issue.

I was running fine with both mods, then I got hit by this bug. Is there anything I can do to restore ? I removed carry-on. But the chunk in question just crashes any client. I believe a check on https://github.com/copygirl/WearableBackpacks/blob/master/src/main/java/net/mcft/copy/backpacks/block/BlockBackpack.java#L81 would prevent it from breaking the client.

Is there a command I can run on the server to destroy the backpacks?

-edit-

I ended up using worldedit /lrbuild air air command to destroy the backpack from long distance.

That sounds like the TileEntityBackpack.facing somehow ended up being an invalid facing. Do you know how the backpack was placed? Did anything happen with it? Machine interaction? WorldEdit?

(I don't work on WBs anymore, I figure I'm going to ask some follow up questions so the current maintainers will have more information once they get around to working on the mod again.)

Hi! Sorry for TRIPLE posting, but I believe I found and solved the issue!
We have a mod called 'Carry-On' installed, and it allows people to pick up entities, and subsequently backpacks.
What would happen, was since the keys were the same for picking up entities, and putting the backpack on, it would bug out. Players would try to equip their backpacks, but accidentally pick them up instead, crashing the client, and sometimes the server.
Simply changing the controls to a different keybind fixes all of the issues.
Thank you for replying earlier, sorry that this turned out to be a massive waste of time, I'm just glad I figured it out lol.

When in crashed me, it was just sitting on a wooden planks block, it was near thaumcraft things, but not connected to anything whatsoever.
I saw the backpack, it was facing towards me, my game crashed, then i was unable to reconnect to the server because it would crash before it finished loading the world.
https://pastebin.com/cFWdPsWA here's a pastebin of the full crash report if that helps at all. I DO have optifine installed and I'm wondering if it might be that.

Apologies for double posting, but now we are getting server crashes.
https://pastebin.com/anssHM6L
I don't know if this is still backpacks, but everytime my friend tries to join, the server crashes.
I'm assuming it's backpacks from that being at the top of the error.

Aight so my friend and I decided to try and test some things on a new world, this happened
https://pastebin.com/SjjmbK86
I believe it is the exact same crash, happened when he right-clicked a backpack to open it.
I'd been placed a bunch of different backpacks facing different ways to see if that did anything also.
My friend also had a backpack on while also right-clicking a backpack on the ground.

https://pastebin.com/9AdkPGAe here's my config file in case that is needed, I'm going to change somethings to see if I can fix the issue at all.

Mkay so we've come to the conclusion that the issue is when a backpack is placed, and the chunk unloaded. Then when a player walks back into said chunk, it causes the crashes.
We installed WorldEdit specifically to test this, and using world edit to delete the backpack one chunk over fixed the crashing issues.
Every other usage of the backpacks works fine, we just cannot place them as a block in the world, then leave them there, without them causing issues.

Or just don't use mods which don't require explicit whitelisting on tile entities, or blacklist backpacks in Carry On.

how do I blacklist backpacks?

@HentaiHamster Check the CarryOn config file. The block ID for backpacks is wearablebackpacks:backpack.