Please help, my server keeps closing after I join it

[frostyblizzard5]

I've been trying to use spongeforge 1.12.2 to use mods on my server, and it works for like 2 hours but after that I get kicked and whenever I try to join back I get kicked and the server immediately closes. If I reset the world it would be fixed for 2 hours but would also crash and repeat the cycle. This is what the crash log says:

---- Minecraft Crash Report ----

WARNING: coremods are present:
  IvToolkit (IvToolkit-1.3.3-1.12.jar)
  SpongeCoremod (spongeforge-1.12.2-2838-7.3.0.jar)
Contact their authors BEFORE contacting forge

// Surprise! Haha. Well, this is awkward.

Time: 12/12/21 3:34 AM
Description: Exception in server tick loop

java.lang.NullPointerException: Exception in server tick loop
    at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:784)
    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)

Does anybody know a fix to this?