Server Closed by crash

My server is with mods 1.12.2 it was working good for 3 days but today after 10 mins of playing it says "Server Closed" and this was the error of the crash i need help to know what it and solve it if possible

java.util.ConcurrentModificationException: null
at java.util.HashMap$HashIterator.nextNode(HashMap.java:1445) ~[?:1.8.0_222]
at java.util.HashMap$KeyIterator.next(HashMap.java:1469) ~[?:1.8.0_222]
at net.minecraft.entity.EntityTracker.func_72788_a(EntityTracker.java:309) ~[ol.class:?]
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:779) ~[MinecraftServer.class:?]
at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:397) ~[nz.class:?]
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:668) ~[MinecraftServer.class:?]
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:526) [MinecraftServer.class:?]
at java.lang.Thread.run(Thread.java:748) [?:1.8.0_222]

This is the full register of the time i player now and it have the same error https://mclo.gs/C9Hujx6

I generated a new one but it still happening

There is no plugins is a forge server

// Oops.

Time: 6/19/20 1:14 PM

Description: Exception in server tick loop

java.util.ConcurrentModificationException

at java.util.HashMap$HashIterator.nextNode(HashMap.java:1445)

at java.util.HashMap$KeyIterator.next(HashMap.java:1469)

at net.minecraft.entity.EntityTracker.func_72788_a(EntityTracker.java:290)

at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:779)

at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:397)

at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:668)

at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:526)

at java.lang.Thread.run(Thread.java:748)

I got this new error in the ticks is there a way to solve it?