com.google.gson.JsonSyntaxException: com.google.gson.stream.MalformedJsonException: Unterminated object at line 141 column 8 path $.pools[0].entries[0].
at com.google.gson.Gson.fromJson(Gson.java:902)
at com.google.gson.Gson.fromJson(Gson.java:852)
at com.google.gson.Gson.fromJson(Gson.java:801)
at com.google.gson.Gson.fromJson(Gson.java:773)
at com.someguyssoftware.gottschcore.loot.LootTableMaster2.loadLootTable(LootTableMaster2.java:502)
at com.someguyssoftware.gottschcore.loot.LootTableMaster2.isWorldDataVersionCurrent(LootTableMaster2.java:331)
at com.someguyssoftware.treasure2.loot.TreasureLootTableMaster2.access$000(TreasureLootTableMaster2.java:45)
at com.someguyssoftware.treasure2.loot.TreasureLootTableMaster2$1.visitFile(TreasureLootTableMaster2.java:333)
at com.someguyssoftware.treasure2.loot.TreasureLootTableMaster2$1.visitFile(TreasureLootTableMaster2.java:296)
at java.nio.file.Files.walkFileTree(Files.java:2670)
at java.nio.file.Files.walkFileTree(Files.java:2742)
at com.someguyssoftware.treasure2.loot.TreasureLootTableMaster2.moveLootTables(TreasureLootTableMaster2.java:296)
at com.someguyssoftware.treasure2.loot.TreasureLootTableMaster2.register(TreasureLootTableMaster2.java:182)
at com.someguyssoftware.treasure2.loot.TreasureLootTableRegistry.register(TreasureLootTableRegistry.java:28)
at com.someguyssoftware.treasure2.eventhandler.WorldEventHandler.onWorldLoad(WorldEventHandler.java:64)
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler_4856_WorldEventHandler_onWorldLoad_Load.invoke(.dynamic)
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:90)
at net.minecraftforge.fml.common.eventhandler.EventBus.post(EventBus.java:182)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at net.optifine.reflect.Reflector.call(Reflector.java:976)
at net.optifine.reflect.Reflector.postForgeBusEvent(Reflector.java:1251)
at net.optifine.reflect.Reflector.postForgeBusEvent(Reflector.java:1237)
at net.minecraft.server.integrated.IntegratedServer.loadAllWorlds(IntegratedServer.java:151)
at net.minecraft.server.integrated.IntegratedServer.init(IntegratedServer.java:233)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:486)
at java.lang.Thread.run(Thread.java:745)
Caused by: com.google.gson.stream.MalformedJsonException: Unterminated object at line 141 column 8 path $.pools[0].entries[0].
at com.google.gson.stream.JsonReader.syntaxError(JsonReader.java:1559)
at com.google.gson.stream.JsonReader.doPeek(JsonReader.java:491)
at com.google.gson.stream.JsonReader.skipValue(JsonReader.java:1224)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:218)
at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.read(TypeAdapterRuntimeTypeWrapper.java:41)
at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:82)
at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:61)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.read(ReflectiveTypeAdapterFactory.java:129)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:220)
at com.google.gson.Gson.fromJson(Gson.java:887)
... 28 more

Upon loading a world I get the above report which identifies Treasure2! as the issue. It seems to happen randomly but I am now unable to join the world.
I can create a world no problem. I can load most worlds too.
However some worlds just seem to crash on startup everytime for seemingly no reason.

Downpatching to version 1.12 of the mod has temporarily fixed fixed the problem so it seems to be a recent issue

Turns out deleting the [World save]/data/loot_tables/treasure2/treasure folder fixes the issue, but only until the next load. That or downgrading to version 1.12 as stated above

If this is v1.15, try deleting all the loot tables from [config]/treasure2/loot_tables AND [World save]/data/loot_tables/treasure2, as the world save version is generated from the config version.