To reproduce:
1. Open attached Unity project "aeRemainAsShifting.zip"
2. Open "proto" scene in "SCENES" folder
3. Enable Steam Audio Manager Settings GameObject in Hierarchy
4. Start Play Mode

Result: at this point Unity always crashes

Regression first introduced in: 5.6.3f1
Reproduced on: 5.6.3f1
Not reproduced on: 5.5.4p2, 5.6.2p4

Cannot test on 2017.1, 2017.2 and 2017.3 because of an ambiguous reference error in PhotonNetwork/LoadbalancingPeer.cs

Note: Not reproducible with a different new scene
Note: Crashes even if all other GameObjects in the scene are disabled
Note: Crashes even if SteamAudioManager is inactive