When opening an anti-barrel in the modpack "Modern Skyblock 3 Departed" version "3.5.0" I got the following error (my guess is that there were more unique types (probably with enchantments and such) than expected):

java.lang.IllegalArgumentException: Payload may not be larger than 32767 bytes
at net.minecraft.network.play.client.CPacketCustomPayload.(CPacketCustomPayload.java:28) ~[lh.class:?]
at net.minecraftforge.fml.common.network.internal.FMLProxyPacket.toC17Packet(FMLProxyPacket.java:142) ~[FMLProxyPacket.class:?]
at net.minecraftforge.fml.common.network.handshake.NetworkDispatcher.write(NetworkDispatcher.java:533) ~[NetworkDispatcher.class:?]
at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:738) ~[netty-all-4.1.9.Final.jar:4.1.9.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeWriteAndFlush(AbstractChannelHandlerContext.java:801) ~[netty-all-4.1.9.Final.jar:4.1.9.Final]
at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:814) ~[netty-all-4.1.9.Final.jar:4.1.9.Final]
at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:794) ~[netty-all-4.1.9.Final.jar:4.1.9.Final]
at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:831) ~[netty-all-4.1.9.Final.jar:4.1.9.Final]
at io.netty.channel.DefaultChannelPipeline.writeAndFlush(DefaultChannelPipeline.java:1032) ~[netty-all-4.1.9.Final.jar:4.1.9.Final]
at io.netty.channel.AbstractChannel.writeAndFlush(AbstractChannel.java:296) ~[netty-all-4.1.9.Final.jar:4.1.9.Final]
at net.minecraft.network.NetworkManager$4.run(NetworkManager.java:245) [gw$4.class:?]
at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:163) [netty-all-4.1.9.Final.jar:4.1.9.Final]
at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:403) [netty-all-4.1.9.Final.jar:4.1.9.Final]
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:442) [netty-all-4.1.9.Final.jar:4.1.9.Final]
at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:858) [netty-all-4.1.9.Final.jar:4.1.9.Final]
at java.lang.Thread.run(Thread.java:748) [?:1.8.0_144]

Just came here to add that Project Ozone 3 had to remove the anti-barrel due to it corrupting player data/worlds since it can hold more data then Minecraft has hardcoded as a limit to items or whatever.

Guess there has gotta be a much smaller limit so that it doesn't force a chunk to exceed it's hardcoded data limit. (There was a dupe glitch in vanilla minecraft awhile back where you could overload a chunk with written book data and it wouldn't save. Figure it's something very similar.)