I got to the flag with Zoey next to it, but I'm not sure if there was something else I was supposed to do.
I think the smaller, faster shots should've had either a vocalization without any strong attack (such as a long "sssssssssssss") with a somewhat lower volume or the vocalization you used but at a much lower sound volume. That way they wouldn't end up being louder than the stronger spells and it wouldn't be as obvious that a sound clip is being constantly repeated.