Problem/Bug Issue with startup script for linux

Hi! I'm trying to setup a stratup script for my server on my vps, but i'm having a weird problem.

First of all, the script i'm using (not created by me, i've just slightly modified it to adadpt it to my environment):
http://pastebin.com/Fh4BcE2Y

If i manyally type the screen -dmS [...] command which is excecuted in the mc_start function both the screen session and the server starts correctly; if i start the server with the script instead, it immediately stops (log: http://pastebin.com/bQj8KWE3)

The server jar i'm using is the spigot one, but the same effect happens even with the vanilla server jar.
Any ideas?

 

Well, yeah... Right now i'm using a very simple one wrote with my VERY basic skills... The thing is, I might need the complex one someday, so it would be nice if it worked like it should