Annies Tibbers stun area not as large as the outline of the spell.

Just played Annie, and i'm 90% sure 5 times i ultied and stun the enemy was in the area, but did not get stunned. I even looked at the replay at .25x speed and i'm sure that 2 times the enemy was definently in the area of the ult, but at the end of it but they did not get stunned or take damage. I googled the problem and found a reddit post with alot of annie mains complaining and agreeing on the issue. Just wondering if anyone here has noticed this problem ?