[18:35:57] [Server thread/WARN]: Can't keep up! Did the system time change, or is the server overloaded? Running 15047ms behind, skipping 300 tick(s)
[18:36:00] [Server thread/WARN]: Can't keep up! Did the system time change, or is the server overloaded? Running 2012ms behind, skipping 40 tick(s)
[18:36:20] [Server thread/ERROR]: Encountered an unexpected exception
java.util.ConcurrentModificationException
at java.util.HashMap$HashIterator.nextNode(HashMap.java:1437) ~[?:1.8.0_144]
at java.util.HashMap$KeyIterator.next(HashMap.java:1461) ~[?:1.8.0_144]
at net.minecraft.entity.EntityTracker.func_72788_a(EntityTracker.java:280) ~[lp.class:?]
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:721) ~[MinecraftServer.class:?]
at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:387) ~[ld.class:?]
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:613) ~[MinecraftServer.class:?]
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:471) [MinecraftServer.class:?]
at java.lang.Thread.run(Thread.java:748) [?:1.8.0_144]
[18:36:20] [Server thread/ERROR]: This crash report has been saved to: /aternos/server/./crash-reports/crash-2018-02-18_18.36.20-server.txt
[18:36:20] [Server thread/INFO]: Stopping server