Tibbers Only casts on smart cast about 60 percent of the time on new rift

Exaclty what it says in the title. Played a game today in team builder, have ult on smartcast (like with all my champs) and when i hit R it wouldn't always cast. I haven't had this problem with annie any other time, and i had played an ARAM as her just before the TB game.

Not sure if anyone else has had this issue.