Is VIP 50% exp bonus bugged?

The first time I cleared 4-44 , I got 900+ exp with a 2-star rating..

Now I clear it again, I only get 200+ with a 1-star rating..

I got VIP on both times.. my dragon level was 23 for both.

Is this a bug?? or I only get the 50% exp bonus on the first time I clear it?

New stars add bonus XP... So the first time you do a stage has the bonus and your second does not.
If you three star that stage later on you will receive bonus XP again