UUID and multiple servers

So i have some servers with the latest bukkit-connect & golilypad.
I don;t know how but all server have different uuids for players.

And to be honest i dont know the uuid system very well.
If i am correct you get a UUID by player right?

Can someone explain that with a possible fix :3 ?

Edit:
I don't understand that there is not very good documented or there is no discussion topic.
I like to change that

The servers MUST have "online-mode: true" in the server properties. My UUID is bc55e something, but with online-mode set to false, its like 45 something something.

Yes i have thats the point! 4 servers and all differend uuids. I checked and there are realy online-mode. Using SpigotMC #git-Spigot-1423 (MC: 1.7.8)

Edit:
Just updated to git-Spigot-1434 (MC: 1.7.9)

Edit2:
So i found this "tool": https://uuid.swordpvp.com/uuid/<username>
As i put my username there the uuid is f90d1b0de926417f9f1da9f7f3fa50c3
When i join the hub server is has my correct uuid, from the usercache.json i guess.
But if i join another server where i deleted the usercache i get a different uuid!
17.04 22:55:38 [Server] INFO UUID of player TakeMeNL is a59ade62-bbbc-3c9b-bc63-da56ce5fb61f
Why Why Why!

Confirmed on my end as well. #74 proxy and #64 connect with spigot #1434 claims my uuid begins with 48a54932- when it is actually b5ccebaa-.

Looking for a solution.

Edit: Spigot/Craftbukkit appear to print the incorrect UUID. Using a command I can properly retrieve my UUID from the server.