Essentially what the title describes. I was on my server with Adventure-Backpack-Mod-1.7.10-0.8c loaded and I tried to drink water from the a tank that was full of water (it was the Left tank). Once the drink animation finished, I was disconnected from the server with the message "Internal Server Error".

Here's what the server logged:

[Server thread/WARN]: Failed to handle packet for /192.168.2.1:34527 net.minecraft.util.ReportedException: Ticking player at net.minecraft.entity.player.EntityPlayerMP.func_71127_g(EntityPlayerMP.java:349) ~[mw.class:?] at net.minecraft.network.NetHandlerPlayServer.func_147347_a(NetHandlerPlayServer.java:303) ~[nh.class:?] at net.minecraft.network.play.client.C03PacketPlayer.func_148833_a(SourceFile:137) ~[jd.class:?] at net.minecraft.network.play.client.C03PacketPlayer.func_148833_a(SourceFile:8) ~[jd.class:?] at net.minecraft.network.NetworkManager.func_74428_b(NetworkManager.java:212) ~[ej.class:?] at net.minecraft.network.NetworkSystem.func_151269_c(NetworkSystem.java:165) [nc.class:?] at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:659) [MinecraftServer.class:?] at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:334) [lt.class:?] at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:547) [MinecraftServer.class:?] at fastcraft.u.a(F:289) [fastcraft-1.25.jar:?] at fastcraft.H.aq(F:36) [fastcraft-1.25.jar:?] at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:396) [MinecraftServer.class:?] at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:685) [li.class:?] Caused by: java.lang.NoSuchFieldError: field_70118_ct at com.darkona.adventurebackpack.fluids.effects.WaterEffect.affectDrinker(WaterEffect.java:30) ~[WaterEffect.class:?] at com.darkona.adventurebackpack.fluids.FluidEffectRegistry.executeFluidEffectsForFluid(FluidEffectRegistry.java:111) ~[FluidEffectRegistry.class:?] at com.darkona.adventurebackpack.common.ServerActions.setFluidEffect(ServerActions.java:94) ~[ServerActions.class:?] at com.darkona.adventurebackpack.item.ItemHose.func_77654_b(ItemHose.java:423) ~[ItemHose.class:?] at net.minecraft.item.ItemStack.func_77950_b(Unknown Source) ~[add.class:?] at net.minecraft.entity.player.EntityPlayer.func_71036_o(Unknown Source) ~[yz.class:?] at net.minecraft.entity.player.EntityPlayerMP.func_71036_o(EntityPlayerMP.java:866) ~[mw.class:?] at net.minecraft.entity.player.EntityPlayer.func_70071_h_(Unknown Source) ~[yz.class:?] at net.minecraft.entity.player.EntityPlayerMP.func_71127_g(EntityPlayerMP.java:295) ~[mw.class:?] at net.minecraft.network.NetHandlerPlayServer.func_147347_a(NetHandlerPlayServer.java:303) ~[nh.class:?] at net.minecraft.network.play.client.C03PacketPlayer.func_148833_a(SourceFile:137) ~[jd.class:?] at net.minecraft.network.play.client.C03PacketPlayer.func_148833_a(SourceFile:8) ~[jd.class:?] at net.minecraft.network.NetworkManager.func_74428_b(NetworkManager.java:212) ~[ej.class:?] at net.minecraft.network.NetworkSystem.func_151269_c(NetworkSystem.java:165) ~[nc.class:?] at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:659) ~[MinecraftServer.class:?] at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:334) ~[lt.class:?] at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:547) ~[MinecraftServer.class:?] ... 2 more [23:43:10] [Server thread/INFO]: MrPieGaming lost connection: TextComponent{text='Internal server error', siblings=[], style=Style{hasParent=false, color=null, bold=null, italic=null, underlined=null, obfuscated=null, clickEvent=null, hoverEvent=null}} [23:43:10] [Server thread/INFO]: MrPieGaming left the game