I created a world with some mods including this one, i played in this world for days and everything was fine, until today.
I opened my world and i started playing like normal, then I closed it to do something else, and when i tried to reopen it... well it didn't load anymore.
In the log i found out that the cause was this mod (if i remove only this mod the world works again), but it didn't cause me any trouble before, and i played with it for days before this problem showed up.

[05apr2021 14:53:33.899] [Server thread/ERROR] [net.minecraft.server.MinecraftServer/]: Encountered an unexpected exception
net.minecraftforge.fml.config.ConfigFileTypeHandler$ConfigLoadingException: Failed loading config file travelersbackpack-server.toml of type SERVER for modid travelersbackpack
at net.minecraftforge.fml.config.ConfigFileTypeHandler.lambda$reader$1(ConfigFileTypeHandler.java:61) ~[?:?]
at net.minecraftforge.fml.config.ConfigFileTypeHandler$$Lambda$4229/232092461.apply(Unknown Source) ~[?:?]
at net.minecraftforge.fml.config.ConfigTracker.openConfig(ConfigTracker.java:104) ~[?:?]
at net.minecraftforge.fml.config.ConfigTracker.lambda$loadConfigs$1(ConfigTracker.java:83) ~[?:?]
at net.minecraftforge.fml.config.ConfigTracker$$Lambda$4228/717306366.accept(Unknown Source) ~[?:?]
at java.lang.Iterable.forEach(Iterable.java:75) ~[?:1.8.0_51]
at java.util.Collections$SynchronizedCollection.forEach(Collections.java:2062) ~[?:1.8.0_51]
at net.minecraftforge.fml.config.ConfigTracker.loadConfigs(ConfigTracker.java:83) ~[?:?]
at net.minecraftforge.fml.server.ServerLifecycleHooks.handleServerAboutToStart(ServerLifecycleHooks.java:95) ~[?:?]
at net.minecraft.server.integrated.IntegratedServer.func_71197_b(IntegratedServer.java:59) ~[?:?]
at net.minecraft.server.MinecraftServer.func_240802_v_(MinecraftServer.java:621) [?:?]
at net.minecraft.server.MinecraftServer.func_240783_a_(MinecraftServer.java:232) [?:?]
at net.minecraft.server.MinecraftServer$$Lambda$6159/944345401.run(Unknown Source) [?:?]
at java.lang.Thread.run(Thread.java:745) [?:1.8.0_51]
Caused by: com.electronwill.nightconfig.core.io.ParsingException: Not enough data available
at com.electronwill.nightconfig.core.io.ParsingException.notEnoughData(ParsingException.java:22) ~[core-3.6.3.jar:?]
at com.electronwill.nightconfig.core.io.ReaderInput.directReadChar(ReaderInput.java:36) ~[core-3.6.3.jar:?]
at com.electronwill.nightconfig.core.io.AbstractInput.readChar(AbstractInput.java:49) ~[core-3.6.3.jar:?]
at com.electronwill.nightconfig.core.io.AbstractInput.readCharsUntil(AbstractInput.java:123) ~[core-3.6.3.jar:?]
at com.electronwill.nightconfig.toml.TableParser.parseKey(TableParser.java:166) ~[toml-3.6.3.jar:?]
at com.electronwill.nightconfig.toml.TableParser.parseDottedKey(TableParser.java:145) ~[toml-3.6.3.jar:?]
at com.electronwill.nightconfig.toml.TableParser.parseNormal(TableParser.java:55) ~[toml-3.6.3.jar:?]
at com.electronwill.nightconfig.toml.TomlParser.parse(TomlParser.java:44) ~[toml-3.6.3.jar:?]
at com.electronwill.nightconfig.toml.TomlParser.parse(TomlParser.java:37) ~[toml-3.6.3.jar:?]
at com.electronwill.nightconfig.core.io.ConfigParser.parse(ConfigParser.java:113) ~[core-3.6.3.jar:?]
at com.electronwill.nightconfig.core.io.ConfigParser.parse(ConfigParser.java:219) ~[core-3.6.3.jar:?]
at com.electronwill.nightconfig.core.io.ConfigParser.parse(ConfigParser.java:202) ~[core-3.6.3.jar:?]
at com.electronwill.nightconfig.core.file.WriteSyncFileConfig.load(WriteSyncFileConfig.java:73) ~[core-3.6.3.jar:?]
at com.electronwill.nightconfig.core.file.AutosaveCommentedFileConfig.load(AutosaveCommentedFileConfig.java:85) ~[core-3.6.3.jar:?]
at net.minecraftforge.fml.config.ConfigFileTypeHandler.lambda$reader$1(ConfigFileTypeHandler.java:57) ~[?:?]
... 13 more
[05apr2021 14:53:33.906] [Server thread/FATAL] [net.minecraftforge.common.ForgeMod/]: Preparing crash report with UUID 2e4963fd-976e-4ad5-b82e-1f03fa67d1ec

Is there some solution?

Hmm, I don't know what may cause this
Have you changed any config values? If not try deleting traveler's backpack server config from world folder

Any informations?