A lot of these, then hang:
[11:04:25] [Spigot Watchdog Thread/ERROR]: Current Thread: IO-Worker-101
[11:04:25] [Spigot Watchdog Thread/ERROR]: PID: 547 | Suspended: false | Native: false | State: RUNNABLE
[11:04:25] [Spigot Watchdog Thread/ERROR]: Thread is waiting on monitor(s):
[11:04:25] [Spigot Watchdog Thread/ERROR]: Locked on:net.minecraft.world.level.chunk.storage.RegionFile.a(RegionFile.java:333)
[11:04:25] [Spigot Watchdog Thread/ERROR]: Stack:
[11:04:25] [Spigot Watchdog Thread/ERROR]: [email protected]/sun.nio.ch.FileDispatcherImpl.pwrite0(Native Method)
[11:04:25] [Spigot Watchdog Thread/ERROR]: [email protected]/sun.nio.ch.FileDispatcherImpl.pwrite(FileDispatcherImpl.java:68)
[11:04:25] [Spigot Watchdog Thread/ERROR]: [email protected]/sun.nio.ch.IOUtil.writeFromNativeBuffer(IOUtil.java:130)
[11:04:25] [Spigot Watchdog Thread/ERROR]: [email protected]/sun.nio.ch.IOUtil.write(IOUtil.java:76)
[11:04:25] [Spigot Watchdog Thread/ERROR]: [email protected]/sun.nio.ch.IOUtil.write(IOUtil.java:67)
[11:04:25] [Spigot Watchdog Thread/ERROR]: [email protected]/sun.nio.ch.FileChannelImpl.writeInternal(FileChannelImpl.java:878)
[11:04:25] [Spigot Watchdog Thread/ERROR]: [email protected]/sun.nio.ch.FileChannelImpl.write(FileChannelImpl.java:864)
[11:04:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.world.level.chunk.storage.RegionFile.d(RegionFile.java:380)
[11:04:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.world.level.chunk.storage.RegionFile.a(RegionFile.java:333)
[11:04:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.world.level.chunk.storage.RegionFile$ChunkBuffer.close(RegionFile.java:439)
[11:04:25] [Spigot Watchdog Thread/ERROR]: [email protected]/java.util.zip.DeflaterOutputStream.close(DeflaterOutputStream.java:240)
[11:04:25] [Spigot Watchdog Thread/ERROR]: [email protected]/java.io.FilterOutputStream.close(FilterOutputStream.java:188)
[11:04:25] [Spigot Watchdog Thread/ERROR]: [email protected]/java.io.FilterOutputStream.close(FilterOutputStream.java:188)
[11:04:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.world.level.chunk.storage.RegionFileCache.a(RegionFileCache.java:155)
[11:04:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.world.level.chunk.storage.IOWorker.a(SourceFile:174)
[11:04:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.world.level.chunk.storage.IOWorker.a(SourceFile:164)
[10:12:23] [Server thread/INFO]: Heads for Minesweeper found in 10.080s.
[11:04:25] [Spigot Watchdog Thread/ERROR]: [email protected]/sun.nio.ch.FileChannelImpl.writeInternal(FileChannelImpl.java:878)
[11:04:25] [Spigot Watchdog Thread/ERROR]: [email protected]/sun.nio.ch.FileChannelImpl.write(FileChannelImpl.java:864)
[11:04:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.world.level.chunk.storage.RegionFile.d(RegionFile.java:380)
[11:04:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.world.level.chunk.storage.RegionFile.a(RegionFile.java:333)
[10:08:24] [ServerMain/INFO]: Environment: authHost='https://authserver.mojang.com', accountsHost='https://api.mojang.com', sessionHost='https://sessionserver.m[11:04:25] [Spigot Watchdog Thread/ERROR]: [email protected]/sun.nio.ch.FileChannelImpl.writeInternal(FileChannelImpl.java:878)
[11:04:25] [Spigot Watchdog Thread/ERROR]: [email protected]/sun.nio.ch.FileChannelImpl.write(FileChannelImpl.java:864)
[11:04:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.world.level.chunk.storage.RegionFile.d(RegionFile.java:380)
[11:04:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.world.level.chunk.storage.RegionFile.a(RegionFile.java:333)
[11:04:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.world.level.chunk.storage.RegionFile$ChunkBuffer.close(RegionFile.java:439)
[11:04:25] [Spigot Watchdog Thread/ERROR]: [email protected]/java.util.zip.DeflaterOutputStream.close(DeflaterOutputStream.java:240)
[11:04:25] [Spigot Watchdog Thread/ERROR]: [email protected]/java.io.FilterOutputStream.close(FilterOutputStream.java:188)
[11:04:25] [Spigot Watchdog Thread/ERROR]: [email protected]/java.io.FilterOutputStream.close(FilterOutputStream.java:188)
[11:04:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.world.level.chunk.storage.RegionFileCache.a(RegionFileCache.java:155)
[11:04:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.world.level.chunk.storage.IOWorker.a(SourceFile:174)
[11:04:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.world.level.chunk.storage.IOWorker.a(SourceFile:164)
[11:04:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.world.level.chunk.storage.IOWorker$$Lambda$6534/0x000000080209d2e0.run(Unknown Source)
[11:04:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.util.thread.PairedQueue$b.run(SourceFile:59)
[11:04:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.util.thread.ThreadedMailbox.h(SourceFile:91)
[11:04:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.util.thread.ThreadedMailbox.a(SourceFile:146)
[11:04:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.util.thread.ThreadedMailbox.run(SourceFile:102)
[11:04:25] [Spigot Watchdog Thread/ERROR]: [email protected]/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)
[11:04:25] [Spigot Watchdog Thread/ERROR]: [email protected]/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
[11:04:25] [Spigot Watchdog Thread/ERROR]: [email protected]/java.lang.Thread.run(Thread.java:833)