Buffer underflow. Error

Anyway I have 2 similar clients but get an error on the second one.

Server: http://hastebin.com/iqiwuzukif.sql
Client 1 (Works): http://hastebin.com/gukidequfi.vbs
Client 2 (Error): http://hastebin.com/pupefoqeja.md

Codes:
Client 1 (Works): http://hastebin.com/jadawuzava.vbs
Client 2 (Error): http://hastebin.com/cuvuheyena.vbs

There is a small difference:
Client 1: Java Application
Client 2: Spigot Plugin (https://www.spigotmc.org/), Modded Server Software for Minecraft Servers (dont tell me a kid ;))

Im very thankful for any answer! <3