PLEASE FIX: Cannot mute parts in iPhone App

Hello,
I use the iPhone App constantly for my job, as I teach choir. My favorite features were 1) The ability to mute/change the volume on separate tracks and 2) the ability to click anywhere in the music to begin playing.
Since the previous update 2/3ish weeks ago, both of those functions have stopped. When I try to mute a track, it still continues to play. I have tried everything to fix it, including deleting and redownloading the App. In addition, you now have to "slide" the bar to start where you want and it takes WAY too long to find the spot you need in large scores. I miss the tap and there you are function.

Please consider fixing both of these problems in newer updates. The functionality of the app is now lost for me.

Thank you!