If you want to change the "Gain& Expo Tuning" values with GERMAN LOCALE SETINGS, you can't change the values. (Android version)
For example it displays "0,50" (comma) and if you change it to "0,40" the value turns red and your change is not accepted.
If you enter "0.40" (point) the value turns blue and is displayed as "0,40". So you can only enter english locale values although it is displayed in the correct german locale format.
Very confusing.

I'm sorry you had an issue, can you post a screenshot and I will forward it to the app team.