I use the LingQ app for iOS on iPhone 6s Plus and the most recent update has broken the volume setting. I used to be able to change the app volume at any time using the +/- volume button, but now if the phone volume is changed, the app volume doesn’t change with it. The only way to change app volume is to click on a word first and then there is ~1 second window which allows the app volume to be changed with the phone volume.