RAD server modpack drops an error while I try to join

This is what console threw out after crashing

> 2020-07-01 18:34:38,739 Server Shutdown Thread ERROR An exception occurred processing Appender Console java.lang.IllegalStateException
    at org.jline.reader.impl.LineReaderImpl.callWidget(LineReaderImpl.java:651)
    at net.minecraftforge.server.terminalconsole.TerminalConsoleAppender.append(TerminalConsoleAppender.java:308)
    at org.apache.logging.log4j.core.config.AppenderControl.tryCallAppender(AppenderControl.java:156)
    at org.apache.logging.log4j.core.config.AppenderControl.callAppender0(AppenderControl.java:129)
    at org.apache.logging.log4j.core.config.AppenderControl.callAppenderPreventRecursion(AppenderControl.java:120)
    at org.apache.logging.log4j.core.config.AppenderControl.callAppender(AppenderControl.java:84)
    at org.apache.logging.log4j.core.appender.rewrite.RewriteAppender.append(RewriteAppender.java:83)
    at org.apache.logging.log4j.core.config.AppenderControl.tryCallAppender(AppenderControl.java:156)
    at org.apache.logging.log4j.core.config.AppenderControl.callAppender0(AppenderControl.java:129)
    at org.apache.logging.log4j.core.config.AppenderControl.callAppenderPreventRecursion(AppenderControl.java:120)
    at org.apache.logging.log4j.core.config.AppenderControl.callAppender(AppenderControl.java:84)
    at org.apache.logging.log4j.core.config.LoggerConfig.callAppenders(LoggerConfig.java:448)
    at org.apache.logging.log4j.core.config.LoggerConfig.processLogEvent(LoggerConfig.java:433)
    at org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:417)
    at org.apache.logging.log4j.core.config.LoggerConfig.logParent(LoggerConfig.java:439)
    at org.apache.logging.log4j.core.config.LoggerConfig.processLogEvent(LoggerConfig.java:434)
    at org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:417)
    at org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:403)
    at org.apache.logging.log4j.core.config.AwaitCompletionReliabilityStrategy.log(AwaitCompletionReliabilityStrategy.java:63)
    at org.apache.logging.log4j.core.Logger.logMessage(Logger.java:146)
    at org.apache.logging.log4j.spi.AbstractLogger.logMessageSafely(AbstractLogger.java:2091)
    at org.apache.logging.log4j.spi.AbstractLogger.logMessage(AbstractLogger.java:1988)
    at org.apache.logging.log4j.spi.AbstractLogger.logIfEnabled(AbstractLogger.java:1960)
    at org.apache.logging.log4j.spi.AbstractLogger.info(AbstractLogger.java:1297)
    at net.minecraft.server.MinecraftServer.func_71260_j(MinecraftServer.java:420)
    at net.minecraft.server.MinecraftServer$4.run(MinecraftServer.java:1579)

This is what crash report said about it

Time: 2020-07-01 18:34:38 CEST
Description: Exception ticking world

java.util.ConcurrentModificationException
    at java.util.LinkedList$ListItr.checkForComodification(Unknown Source)
    at java.util.LinkedList$ListItr.remove(Unknown Source)
    at net.minecraft.server.management.PlayerChunkMap.tick(SourceFile:148)
    at net.minecraft.world.WorldServer.tick(WorldServer.java:227)
    at net.minecraft.server.MinecraftServer.updateTimeLightAndEntities(MinecraftServer.java:756)
    at net.minecraft.server.dedicated.DedicatedServer.updateTimeLightAndEntities(DedicatedServer.java:397)
    at net.minecraft.server.MinecraftServer.tick(MinecraftServer.java:668)
    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:526)
    at java.lang.Thread.run(Unknown Source)

Version of Server Forge is forge-1.12.2-14.23.5.2838-universal and server is running on 1.12.2. Please help, I was trying 3 hours to figure out what's going on, if it's because of some mod but nothing works.