[15:24:42] [Server thread/WARN]: [Parkour] Task #34 for Parkour v1.0 generated an exception
java.util.ConcurrentModificationException: null
	at java.util.HashMap$HashIterator.nextNode(HashMap.java:1442) ~[?:1.8.0_171]
	at java.util.HashMap$KeyIterator.next(HashMap.java:1466) ~[?:1.8.0_171]
	at eu.MarkGyori.Parkour.Parkour$1.run(Parkour.java:48) ~[?:?]
	at org.bukkit.craftbukkit.v1_12_R1.scheduler.CraftTask.run(CraftTask.java:76) ~[server.jar:git-Spigot-642f6d2-fbe3046]
	at org.bukkit.craftbukkit.v1_12_R1.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:361) [server.jar:git-Spigot-642f6d2-fbe3046]
	at net.minecraft.server.v1_12_R1.MinecraftServer.D(MinecraftServer.java:739) [server.jar:git-Spigot-642f6d2-fbe3046]
	at net.minecraft.server.v1_12_R1.DedicatedServer.D(DedicatedServer.java:406) [server.jar:git-Spigot-642f6d2-fbe3046]
	at net.minecraft.server.v1_12_R1.MinecraftServer.C(MinecraftServer.java:679) [server.jar:git-Spigot-642f6d2-fbe3046]
	at net.minecraft.server.v1_12_R1.MinecraftServer.run(MinecraftServer.java:577) [server.jar:git-Spigot-642f6d2-fbe3046]
	at java.lang.Thread.run(Thread.java:748) [?:1.8.0_171]