Issue description

https://gist.github.com/ternsip/bcb55a26b7815692032dc3b8258da12c

Steps to reproduce

1. Open Diamond barrel from IronBarrels with mechanical pipe

Minecraft version

1.16.5 (Latest)

Forge version

36.2.0

Mekanism version

10.0.21 (Latest)

Other relevant versions

No response

If a (crash)log is relevant for this issue, link it here: (It's almost always relevant)

https://gist.github.com/ternsip/bcb55a26b7815692032dc3b8258da12c

This looks like some mod or something corrupted your world or given the crash is client side something is causing it to send the wrong information about tiles/blocks to the client. Not really sure what to suggest as I don't think this has anything to do with Mekanism beyond the fact that it thinks one of our tiles is where a metal barrel is.

Thanks
Yes crash happened on client side. I mean that barrel with something corrupted stored on server-side world and any client that has come to that barrel and opened it falls into that kind of crash.
Maybe you are right about mowzie mobs. I just can't leave that bug without proper solution.
I sent it to bobmowzie mob

That was server side. All clients who tried to open that barrel with mechanichal pipe had such crash. After destroying that barrel items poped out and the bug has gone. Perhaps it's on mechanism side because author of iron barrels responded nagative.
In fact bug is not fixed. I am not sure if some mods corrupt something. Perhaps some method do wrong things with class casting. So I suggest to reopen it. Not considering it as resolved by myself.
It's either your mod or metal barrels we need to understand.

The crash happened ON the client side, doesn't matter that you were connected to a server.

The bug could have been caused by a vanilla or Forge issue, but there's not enough info to go on. It is certainly unlikely to be anything Mek or Iron Barrels did

The end result is that SOMETHING caused the normal association between block and TileEntity/BlockEntity to break down.

There is nothing either mod can do. You could check with mowziesmobs since it's happened inside their event handler

I mean there is also a fair chance if you have a bunch of mods it may just be mojang's bug of the fact that SMultiBlockChangePacket doesn't encode things properly from what some people have mentioned to me at one point which then just makes it so that there is a different block there. If I had to guess that may just be it given the crash is client side and not server side (though maybe the server has the mismatch as well and it just isn't calling the problematic method)