When I'm in an Avatar World it crashes randomly.
Crash Report Below
---- Minecraft Crash Report ----
// Why did you do that?

Time: 6/8/20 12:18 PM
Description: Exception in server tick loop

java.lang.NoSuchMethodError: net.minecraftforge.fml.relauncher.ReflectionHelper.getPrivateValue(Ljava/lang/Class;Ljava/lang/Object;Ljava/lang/String;Ljava/lang/String;)Ljava/lang/Object;
at com.crowsofwar.avatar.common.util.AvatarUtils.(AvatarUtils.java:61)
at com.crowsofwar.avatar.common.data.BendingData.writeToNbt(BendingData.java:511)
at com.crowsofwar.avatar.common.data.AvatarPlayerData.writePlayerDataToNBT(AvatarPlayerData.java:81)
at com.crowsofwar.gorecore.data.PlayerData.writeToNBT(PlayerData.java:128)
at com.crowsofwar.gorecore.data.PlayerData$1.writeV(PlayerData.java:61)
at com.crowsofwar.gorecore.data.PlayerData$1.writeV(PlayerData.java:33)
at com.crowsofwar.gorecore.util.GoreCoreNBTUtil.writeMapToNBT(GoreCoreNBTUtil.java:161)
at com.crowsofwar.gorecore.data.WorldDataPlayers.func_189551_b(WorldDataPlayers.java:55)
at com.crowsofwar.avatar.common.data.AvatarWorldData.func_189551_b(AvatarWorldData.java:88)
at net.minecraft.world.storage.MapStorage.func_75747_a(SourceFile:92)
at net.minecraft.world.storage.MapStorage.func_75744_a(SourceFile:78)
at net.minecraft.world.WorldServer.func_73042_a(WorldServer.java:1053)
at net.minecraft.world.WorldServer.func_73044_a(WorldServer.java:1001)
at net.minecraft.server.MinecraftServer.func_71267_a(MinecraftServer.java:407)
at net.minecraft.server.integrated.IntegratedServer.func_71267_a(IntegratedServer.java:252)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:688)
at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:185)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:523)
at java.lang.Thread.run(Thread.java:745)

A detailed walkthrough of the error, its code path and all known details is as follows:

-- System Details --
Details:
Minecraft Version: 1.12
Operating System: Windows 10 (amd64) version 10.0
Java Version: 1.8.0_51, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 575806232 bytes (549 MB) / 1476395008 bytes (1408 MB) up to 2147483648 bytes (2048 MB)
JVM Flags: 8 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx2G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=32M
IntCache: cache: 1, tcache: 1, allocated: 12, tallocated: 94
FML: MCP 9.40 Powered by Forge 14.21.1.2387 7 mods loaded, 7 mods active
States: 'U' = Unloaded 'L' = Loaded 'C' = Constructed 'H' = Pre-initialized 'I' = Initialized 'J' = Post-initialized 'A' = Available 'D' = Disabled 'E' = Errored
UCHIJAAAA minecraft{1.12} [Minecraft] (minecraft.jar)
UCHIJAAAA mcp{9.19} [Minecraft Coder Pack] (minecraft.jar)
UCHIJAAAA FML{8.0.99.99} [Forge Mod Loader] (forge-1.12-14.21.1.2387.jar)
UCHIJAAAA forge{14.21.1.2387} [Minecraft Forge] (forge-1.12-14.21.1.2387.jar)
UCHIJAAAA mercurius_updater{1.0} [mercurius_updater] (MercuriusUpdater-1.12.jar)
UCHIJAAAA gorecore{1.12.2-0.4.5} [GoreCore] (avatarmod-1.5.17-alpha.jar)
UCHIJAAAA avatarmod{1.5.17-alpha} [Avatar Mod: Out of the Iceberg] (avatarmod-1.5.17-alpha.jar)
Loaded coremods (and transformers):
GL info: ERROR RuntimeException: No OpenGL context found in the current thread.
Profiler Position: N/A (disabled)
Player Count: 1 / 8; [EntityPlayerMP['Stonebend'/2519, l='New World', x=163.76, y=63.78, z=220.03]]
Type: Integrated Server (map_client.txt)
Is Modded: Definitely; Client brand changed to 'fml,forge'

I redownloaded the latest version of Forge 1.12 and it still crashes

You need to update your forge.

Same thing happens to me they should just make it available for the newest version of forge

This is a crash which only happens when you have an incorrect Forge version. If you still experience crashes, please open a new ticket with an updated crash report.