Missing battle sounds from the game

I am playing with Delta emulator on iPad, when I started changing my device's date and time settings to rematch certain trainers for E4 grinding, some sound effects like pokemon's cries, certain move sound effects, etc. were not heard, OST and the sounds of clicking buttons were heard just fine. The game just feels incomplete during the battles because of this, and I am fighting the E4.

Any fixes for this?