DarkRP jail positions

I lately started a DarkRP Server. Now I am trying to add jail positions to the map i recently put on my Server. I use the command “/jailpos” to make my first jail position. So far so good.
(there is also this message popping up saying “You have removed all jail positions and you have added a new one here”)
But every time I use the command “/addjailpos” it deletes the old jail position and creates a new one with the same message as if I use “/jailpos”.
Normally it should say something like “You have added one extra jail position” and it should create a new jail position…but it doesn’t.

How can I fix this?