I had 60ish cantina energy and i just refreshed it twice for a 12 cantina aayla secura node. Out of those 2 refreshes and the 60sih energy I already i had I didn't get a single shard. Is it bad luck ?...
I can't really say with certainty but I know sometimes I might sim say 12 battles and get 1 shard then the next 12 I sim I might get 5. So unlucky streaks do happen and usually the game does seem to balance itself out.
If you are concerned maybe screenshot and make notes.