Reproduction Steps:
1. Import attached project.
2. Open "TestScene".
3. Enter Play mode.

Expected results: Audio source volume is the same on all instances.
Actual results: Audio source volume randomly becomes louder on occasion. (video attached)

Reproducible with: 2017.1.0b10, 2017.2.0a4
Not reproducible with: 5.5.4f1, 5.6.2f1.
Regression introduced in: 2017.1.0b9

Notes:
-The GameObject in Hierarchy has a Timer property. This allows to adjust the speed of the audio source's loop.
-The bug is reproducible when the Timer is set to 1. However, it is more frequent when set to around 0.1.
-The bug may also be reproducible on older versions when the Timer is set to a low enough value (for example, 0.01). However, the volume doesn't seem to be as high.