FML detected the backup level.dat is being used

[AlleinSoldat]

I travel a lot so I use my laptop consistently. So, I transfer all of my progress between my laptop and my desktop. The save game I used first on my desktop after update and it's throwing that error. If I click yes on it, it replaces blocks I've places with either air or some random block like stairs. I have attached screenshots. If I revert back to version 1.0.16, everything works just fine on both computers.

Steps to Reproduce (for bugs)

1. Transfer save game from one PC to another
2. Open save in game

Client Information
Modpack Version: 1.0.17
Server/LAN/Single Player: SSP
Optifine Installed: Nope
Shaders Enabled: Nope

[Sunekaer]

what blocks from what mods has been removed?

[TigerWalts]

I have been dealing with the same issue.

It's considering the FML data in level.dat to be invalid. It falls back to the level.dat_old. That one also fails but it retains the Data node but rebuilds the FML and forge nodes. But because it considers the old FML data to be invalid it ignores it and also skips converting block ids in the region files.

Looking at the level.dat file from before and after updating, a lot of id/index numbers that blocks are registered with have changed, there are 6 more blocks and they would all been assigned ids anew.

You may want to check if this is a known issue with certain Forge versions.

EDIT, this is a likely contender: MinecraftForge/FML#524
It's from a few years back but it's related.

---

The issue appears to be that there are too many blocks:

Exception reading C:\Users\tiger\Documents\Minecraft\Instances\StoneBlock (1)\saves\world\level.dat
java.lang.RuntimeException: Invalid id 4096 - maximum id range exceeded.
	at net.minecraftforge.registries.ForgeRegistry.add(ForgeRegistry.java:296)
	at net.minecraftforge.registries.ForgeRegistry.loadIds(ForgeRegistry.java:694)
...

1.0.17 busts the id limit, this causes an Exception which prevents the id remapping from happening.

[tjd46]

I think @TigerWalts is right as if I add https://minecraft.curseforge.com/projects/notenoughids even my old world loads right up fine.
Another alternative might be https://minecraft.curseforge.com/projects/jeid

[Sunekaer]

does it work for you adding https://minecraft.curseforge.com/projects/notenoughids @AlleinSoldat ?

[AlleinSoldat]

Haven't had a chance to try. I was stuck at work all day yesterday. I'll give it a shot right now and report back.

[AlleinSoldat]

Seems to work with the addition of notenoughids. Thanks for the help everyone!

[Sunekaer]

1.0.18