I was struggling to get into BBL the last few seasons and then that nonsense was announced I deleted my BBL SC before rd1. Watched 4 Strikerz games and use to watch every single free to air telecast match.
For a 20 ball innings a dot ball changes your SR by 5 points... in other words it's going to change the SR bracket half the time. Not surprised at all by that. Even for a longer innings it'd happen a few times out of ten, and like you said you're bound to notice them when they happen to your players!