To reproduce:

1. Download and open "repro805679" project from provided link.
2. Open "Main" scene.
3. Open Audio Mixer window and select "NewAudioMixer" mixer in assets.
4. Select "Snapshot_OFF" snapshot and press play.
5. Notice that snapshots transition form "Snapshot_OFF" to "Snapshot_ON" in 5 seconds.
6. After transition exit play mode.
7. Enter play mode again.
8. Notice that transition does not happen from "Snapshot_OFF" even though it is set as start snapshot.

Expected result: Snapshots should always transition from start snapshot even if start snapshot is not selected in AudioMixer window.
Actual result: Snapshots do not transition from start snapshot when start snapshot is not selected in AudioMixer window.

Reproduced with: 2017.1.0b4, 5.6.1f1, 5.5.3p2, 5.4.5p1

Workaround: Each time when entering play mode select the start snapshot.

Notes: Audio mixer seems to transition snapshots not from start snapshot but from selected one.

Verified with 2017.3.0a4