Server Chunk Saving Issues

[dinoswr]

Hello

I have a custom made modpack for me and a few friends and decided to run it on an online host. After numerous lag issues, we decided to install the Performant mod onto the server. After that didn't fix much, I got the exact same world bar Performant on my system and ran the server on my pc and that fixed all the lag.

Whilst running the server, my console gets a message exactly every second, where it fails to save a chunk due to "java.util.concurrent.CompletionException: java.lang.NullPointerException". This failure to save also results in a "soft" dupe where teleporting back and forth to generated loot (e.g End Cities) reloads the previous state of the chest, resulting in the loot being able to get taken out multiple times.

Below is one of the errors I get every second (this happens for multiple chunks at once)

Spoiler

[11Apr2021 14:50:47.754] [Server thread/ERROR] [net.minecraft.world.server.ChunkManager/]: Failed to save chunk [16, 7]
java.util.concurrent.CompletionException: java.lang.NullPointerException
    at java.util.concurrent.CompletableFuture.encodeThrowable(Unknown Source) ~[?:1.8.0_281]
    at java.util.concurrent.CompletableFuture.completeThrowable(Unknown Source) ~[?:1.8.0_281]
    at java.util.concurrent.CompletableFuture.uniAccept(Unknown Source) ~[?:1.8.0_281]
    at java.util.concurrent.CompletableFuture$UniAccept.tryFire(Unknown Source) ~[?:1.8.0_281]
    at java.util.concurrent.CompletableFuture$Completion.run(Unknown Source) ~[?:1.8.0_281]
    at net.minecraft.world.server.ChunkManager.func_223155_b(ChunkManager.java:388) ~[?:?]
    at net.minecraft.world.server.ChunkManager.func_219204_a(ChunkManager.java:366) ~[?:?]
    at net.minecraft.world.server.ServerChunkProvider.func_217207_a(ServerChunkProvider.java:323) ~[?:?]
    at net.minecraft.world.server.ServerWorld.func_72835_b(ServerWorld.java:333) ~[?:?]
    at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:851) ~[?:?]
    at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:291) ~[?:?]
    at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:787) ~[?:?]
    at net.minecraft.server.MinecraftServer.func_240802_v_(MinecraftServer.java:642) ~[?:?]
    at net.minecraft.server.MinecraftServer.func_240783_a_(MinecraftServer.java:232) ~[?:?]
    at java.lang.Thread.run(Unknown Source) [?:1.8.0_281]
Caused by: java.lang.NullPointerException
    at appeng.hooks.TickHandler.onUnloadChunk(TickHandler.java:180) ~[appliedenergistics2:8.3.0-alpha.2]
    at net.minecraftforge.eventbus.EventBus.doCastFilter(EventBus.java:247) ~[eventbus-4.0.0.jar:?]
    at net.minecraftforge.eventbus.EventBus.lambda$addListener$11(EventBus.java:239) ~[eventbus-4.0.0.jar:?]
    at net.minecraftforge.eventbus.EventBus.post(EventBus.java:302) ~[eventbus-4.0.0.jar:?]
    at net.minecraftforge.eventbus.EventBus.post(EventBus.java:283) ~[eventbus-4.0.0.jar:?]
    at net.minecraft.world.server.ChunkManager.func_219185_a(ChunkManager.java:403) ~[?:?]
    ... 13 more

I am unsure if this is caused by Performant's aftermath on the world file or not, as the chunk fails and soft dupe was still present on the online hosted server, but it's still a pretty major issue that prevents me from properly using the console and floods my drive.

I did a bit of looking around the logs but I'm not sure what really causes it due to the mix of unknowns, mods and forge terms. Hopefully though one of you people get it and I can get it resolved soon

Unfortunately the latest.log is 200MB large so I can't attach it to a pastebin, but the debug.log is here. (The last lines have a fatal due to a tick taking too long)

Full modlist is here.

Thanks!