Error EHM

[14:23:54] [Server thread/WARN]: [ExtraHardMode] Task #83 for ExtraHardMode v3.6.5 generated an exception
java.util.ConcurrentModificationException
    at java.util.HashMap$HashIterator.nextNode(Unknown Source) ~[?:1.8.0_60]
    at java.util.HashMap$KeyIterator.next(Unknown Source) ~[?:1.8.0_60]
    at com.extrahardmode.task.WeightCheckTask.run(WeightCheckTask.java:44) ~[?:?]
    at org.bukkit.craftbukkit.v1_8_R3.scheduler.CraftTask.run(CraftTask.java:71) ~[paper_1.8.8.jar:git-PaperSpigot-f6fba00-9935adc]
    at org.bukkit.craftbukkit.v1_8_R3.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:350) [paper_1.8.8.jar:git-PaperSpigot-f6fba00-9935adc]
    at net.minecraft.server.v1_8_R3.MinecraftServer.B(MinecraftServer.java:779) [paper_1.8.8.jar:git-PaperSpigot-f6fba00-9935adc]
    at net.minecraft.server.v1_8_R3.DedicatedServer.B(DedicatedServer.java:378) [paper_1.8.8.jar:git-PaperSpigot-f6fba00-9935adc]
    at net.minecraft.server.v1_8_R3.MinecraftServer.A(MinecraftServer.java:710) [paper_1.8.8.jar:git-PaperSpigot-f6fba00-9935adc]
    at net.minecraft.server.v1_8_R3.MinecraftServer.run(MinecraftServer.java:613) [paper_1.8.8.jar:git-PaperSpigot-f6fba00-9935adc]
    at java.lang.Thread.run(Unknown Source) [?:1.8.0_60]