Here is finally an answer from the Unibet support team:
I can't see anything in the terms & conditions where it says I can only win one prize in this promotion.
Can anyone else read this in the rules?
Anyway, this has become quite annoying and it is more the principle and the slow (prolonged) answer from Unibet that is not really showing goodwill from Unibet's side.
/dissappointed customer of +10 years