Логи сервера покажите, там написано будет, из-за чего это.

Владимир,  

Аналогичная ошибка описана в Баг-Репорте Spigot. ( https://hub.spigotmc.org/jira/browse/SPIGOT-5801 )

Ядро попробуйте поменять.

Владимир, поменял ядро на спигот 1.16.1, зашел на серв, побежал к порталу, кинул пёрл и серв опять упал. Всё тоже самое. 

 Вот логи: 
[23:24:29] [User Authenticator #2/INFO]: UUID of player Shershulia is 196e4fad-db71-374d-a575-3b677ec6d9d1
[23:24:30] [Server thread/INFO]: Shershulia[/95.215.164.163:50401] logged in with entity id 458 at ([world]-1277.0285430343515, 71.0, -3927.334395019561)
[23:31:23] [Server thread/ERROR]: Encountered an unexpected exception
net.minecraft.server.v1_16_R1.ReportedException: Ticking entity
   at net.minecraft.server.v1_16_R1.MinecraftServer.b(MinecraftServer.java:1117) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   at net.minecraft.server.v1_16_R1.DedicatedServer.b(DedicatedServer.java:354) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   at net.minecraft.server.v1_16_R1.MinecraftServer.a(MinecraftServer.java:1007) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   at net.minecraft.server.v1_16_R1.MinecraftServer.v(MinecraftServer.java:846) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   at net.minecraft.server.v1_16_R1.MinecraftServer.lambda$0(MinecraftServer.java:164) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   at java.lang.Thread.run(Thread.java:748) [?:1.8.0_212]
Caused by: java.lang.ClassCastException: net.minecraft.server.v1_16_R1.EntityEnderPearl cannot be cast to net.minecraft.server.v1_16_R1.EntityPlayer
   at net.minecraft.server.v1_16_R1.TileEntityEndGateway.a(TileEntityEndGateway.java:160) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   at net.minecraft.server.v1_16_R1.EntityProjectile.tick(EntityProjectile.java:36) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   at net.minecraft.server.v1_16_R1.EntityEnderPearl.tick(EntityEnderPearl.java:93) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   at net.minecraft.server.v1_16_R1.WorldServer.entityJoinedWorld(WorldServer.java:659) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   at net.minecraft.server.v1_16_R1.World.a(World.java:751) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   at net.minecraft.server.v1_16_R1.WorldServer.doTick(WorldServer.java:394) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   at net.minecraft.server.v1_16_R1.MinecraftServer.b(MinecraftServer.java:1104) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   ... 5 more
[23:31:23] [Server thread/ERROR]:    Cause of unexpected exception was
java.lang.ClassCastException: net.minecraft.server.v1_16_R1.EntityEnderPearl cannot be cast to net.minecraft.server.v1_16_R1.EntityPlayer
   at net.minecraft.server.v1_16_R1.TileEntityEndGateway.a(TileEntityEndGateway.java:160) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   at net.minecraft.server.v1_16_R1.EntityProjectile.tick(EntityProjectile.java:36) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   at net.minecraft.server.v1_16_R1.EntityEnderPearl.tick(EntityEnderPearl.java:93) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   at net.minecraft.server.v1_16_R1.WorldServer.entityJoinedWorld(WorldServer.java:659) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   at net.minecraft.server.v1_16_R1.World.a(World.java:751) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   at net.minecraft.server.v1_16_R1.WorldServer.doTick(WorldServer.java:394) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   at net.minecraft.server.v1_16_R1.MinecraftServer.b(MinecraftServer.java:1104) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   at net.minecraft.server.v1_16_R1.DedicatedServer.b(DedicatedServer.java:354) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   at net.minecraft.server.v1_16_R1.MinecraftServer.a(MinecraftServer.java:1007) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   at net.minecraft.server.v1_16_R1.MinecraftServer.v(MinecraftServer.java:846) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   at net.minecraft.server.v1_16_R1.MinecraftServer.lambda$0(MinecraftServer.java:164) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   at java.lang.Thread.run(Thread.java:748) [?:1.8.0_212]
[23:31:23] [Server thread/ERROR]: This crash report has been saved to: /data/./crash-reports/crash-2020-08-18_23.31.23-server.txt
[23:31:23] [Server thread/INFO]: Stopping server
[23:31:23] [Server thread/INFO]: Saving players
[23:31:23] [Server thread/INFO]: Shershulia lost connection: Server closed
[23:31:23] [Server thread/ERROR]: Exception stopping the server
java.lang.IllegalStateException: Removing entity while ticking!
   at net.minecraft.server.v1_16_R1.WorldServer.removeEntity(WorldServer.java:1081) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   at net.minecraft.server.v1_16_R1.WorldServer.removePlayer(WorldServer.java:1100) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   at net.minecraft.server.v1_16_R1.PlayerList.disconnect(PlayerList.java:444) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   at net.minecraft.server.v1_16_R1.PlayerConnection.a(PlayerConnection.java:1416) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   at net.minecraft.server.v1_16_R1.PlayerConnection.disconnect(PlayerConnection.java:268) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   at net.minecraft.server.v1_16_R1.PlayerList.shutdown(PlayerList.java:1054) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   at net.minecraft.server.v1_16_R1.MinecraftServer.stop(MinecraftServer.java:725) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   at net.minecraft.server.v1_16_R1.DedicatedServer.stop(DedicatedServer.java:644) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   at net.minecraft.server.v1_16_R1.MinecraftServer.v(MinecraftServer.java:887) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   at net.minecraft.server.v1_16_R1.MinecraftServer.lambda$0(MinecraftServer.java:164) ~[craftbukkit.jar:git-Spigot-758abbe-2b00831]
   at java.lang.Thread.run(Thread.java:748) [?:1.8.0_212]
[23:31:23] [Server thread/INFO]: Thread Query Listener stopped

а с последней версией 1.16.2 можете попробовать?

Скачать: spigot-1.16.2.jar

Владимир, поставил. А заходить мне всё равно с 1.16.1, или как это  работает?

заходить с 1.16.2 нужно.

Владимир,  всё, спасибо, переход на версию 1.16.2 помог