Reproduction steps:
1. Open and build the attached project into iOS device.
2. Click "Mic"(Make sure to run some background sound/music in the room).
3. Wait for ~10 seconds.
4. Click "ReplayKit".
5. Wait for ~10 seconds.
6. Click "ReplayKit".
7. Click Play button.
8. View the video and listen the recorded sound.
- Sound is sped up and distorted(Video attached(12:34 PM)).

Reproduced with:
5.5.0f1, 2017.2.0b1
iPod Touch 10.2.1

Not reproducible with:
iPad Mini 4 10.3.2
iPhone SE 9.3
iPhone 6 Plus 8.0