Errors: http://pastebin.com/7Har8wRQ

Forge 2095, happens in server startup log.

Modlist: https://rys.pw/Minecraft#Modlist

This makes no sense. BlockCarvableCarpet does inherit from BlockCarvable. Code

Can you please isolate what other mods besides Chisel are causing this? I'm suspecting a mod causing problems alongside chisel.

I would also like to see a full server log, as opposed to just the exception so I can check for warnings that would have happened earlier.

@Drullkus are carpets not inheriting from BlockCarvable? If so, then the field in ChiselBlocks cannot be of type BlockCarvable.

http://pastebin.com/fBYAHXiN

We're having same issue in our modpack. Common mods are:
ActuallyAdditions
AppleCore
armorplus
AutoRegLib
Baubles
bdlib
Botania
Chameleon
Chisel (obviously)
CookingForBlockheads
CraftingTweaks
FastLeaveDecay
forestry
gendustry
ImmersiveEngineering
InventoryTweaks
jei
journeymap
JurassiCraft
llibrary
MCMultiPart
Morph-o-Tool
Morpheus
NoMoreRecipeConflict
Pam's HarvestCraft
Quark
RoguelikeDungeons
StorageDrawers
TConstruct
thedragoncore
Tinkers' Addons
TrashSlot
Waila
Wawla
worldedit-forge

From the logs, it says:

Caused by: java.lang.IllegalArgumentException: Can not set static team.chisel.common.block.BlockCarvable field team.chisel.common.init.ChiselBlocks.carpet to net.minecraftforge.fml.common.registry.PersistentRegi
stryManager$BlockDummyAir

Looks like BlockDummyAir isn't a BlockCarvable...

Issue is related to the map itself.
Maybe an old chisel registry name isn't converting properly?

Issue is reproduced with just Chisel and Forge provided the map level.dat includes a "chisel:carpet" registered block.
Forge version tested: forge-1.10.2-12.18.1.2094-universal.jar

Here's a level.dat that reproduces the issue (I've renamed one of chisel carpet_xxx blocks to just carpet):
level.zip

That's not a crash

I never claimed it was. It's an error happening in the server startup phase.

Was the bug fixed since you closed the issue?

The error can be ignored. It was caused by downgrading and missing blocks.

So unless I create a new world I will keep seeing this error in the console?

Sadly yes, it is a bug in the Registry/@ObjectHolder system

That's not up to us, Forge manages the registries

Wouldn't it be possible to detect broken blocks and fix them instead of just letting them stay broken?