Disconnecting when i want to join server

Hi. I'm not native English speaker so sorry for my English :D. I have a problem with my mod. I uploaded it on multiplayer server where I play with my mates. I created armors which give (if i have full set) buffs, tools etc. There is one problem.... When i dress up one of armor set server disconnecting me and I can't join server again (because the armor is worn and i have to clear my equipment to connect with server again). Can anybody help me?
Logs from server's console:
Failed to handle packet for 

net.minecraft.util.ReportedException: Ticking player
    at net.minecraft.entity.player.EntityPlayerMP.func_71127_g(EntityPlayerMP.java:459) ~[oq.class:?]
    at net.minecraft.network.NetHandlerPlayServer.redirect$onPlayerTick$zip000(NetHandlerPlayServer.java:2050) ~[pa.class:?]
    at net.minecraft.network.NetHandlerPlayServer.func_73660_a(NetHandlerPlayServer.java:173) ~[pa.class:?]
    at net.minecraftforge.fml.common.network.handshake.NetworkDispatcher$1.func_73660_a(NetworkDispatcher.java:209) ~[NetworkDispatcher$1.class:?]
    at net.minecraft.network.NetworkManager.func_74428_b(NetworkManager.java:285) ~[gw.class:?]
    at net.minecraft.network.NetworkSystem.func_151269_c(NetworkSystem.java:180) [oz.class:?]
    at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:790) inecraftServer.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) inecraftServer.class:?]
    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:526) inecraftServer.class:?]
    at java.lang.Thread.run(Thread.java:748) [?:1.8.0_181]
Caused by: java.lang.NoSuchMethodError: net.minecraft.entity.player.InventoryPlayer.func_70440_f(I)Lnet/minecraft/item/ItemStack;
    at mod.mcreator.mcreator_ytirArmorLeggingsTickEvent.executeProcedure(mcreator_ytirArmorLeggingsTickEvent.java:24) ~creator_ytirArmorLeggingsTickEvent.class:?]
    at mod.mcreator.mcreator_ytirArmor$1.onArmorTick(mcreator_ytirArmor.java:48) ~creator_ytirArmor$1.class:?]
    at net.minecraft.entity.player.InventoryPlayer.func_70429_k(InventoryPlayer.java:371) ~[aec.class:?]
    at net.minecraft.entity.player.EntityPlayer.func_70636_d(EntityPlayer.java:511) ~[aed.class:?]
    at net.minecraft.entity.EntityLivingBase.func_70071_h_(EntityLivingBase.java:2172) ~[vp.class:?]
    at net.minecraft.entity.player.EntityPlayer.func_70071_h_(EntityPlayer.java:234) ~[aed.class:?]
    at net.minecraft.entity.player.EntityPlayerMP.func_71127_g(EntityPlayerMP.java:382) ~[oq.class:?]
    ... 10 more

[11:32:18] [Server thread/ERROR] [Sponge]: The Scheduler tried to run the task Enter Flag Timer Task owned by Plugin{id=universeguard, name=Universe Guard 2, version=2.17, description=An easy to use world protection plugin for Sponge, authors=[JimiIT92, Brycey92, eheimer], source=/home/k17077_s12282/server_12282/./mods/plugins/UniverseGuard-2.17 (1).jar}, but an error occured.
[11:32:18] [Server thread/INFO] [net.minecraft.network.NetHandlerPlayServer]: Arssen_ lost connection: Internal server error