Reproduction steps:
1. Open the attached project.
2. Build and run the 'Test' scene on an iOS device.
3. Minimize the application by pressing the home button.
4. Maximize the application by clicking the application icon.

Crash:

• thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x18)
• frame #0: 0x000000010073c5f4 keenasrunity`::UnloadClip() [inlined] begin at LinkedList.h:137 [opt]

frame #1: 0x000000010073c5f0 keenasrunity`::UnloadClip() at SoundManager.cpp:1212 [opt]
frame #2: 0x0000000100723fa8 keenasrunity`::CloseFMOD() at AudioManager.cpp:1317 [opt]
frame #3: 0x000000010042419c keenasrunity`-[KeenASRBridge unwindAppAudioBeforeAudioInterrupt](self=<unavailable>, _cmd=<unavailable>) at KeenASRBridge.m:47 [opt]
frame #4: 0x00000001009db708 keenasrunity`-[KIOSRecognizer unwindAppAudioBeforeAudioInterruptInAudioController] + 232
frame #5: 0x00000001009b0ef4 keenasrunity`-[KIOSAudioController unwindAppAudioBeforeAudioInterrupt] + 232
...

Reproduced with:
5.6.4p2,
2017.1.2p2,
2017.2.0p1,
2017.3.0b8,
2018.1.0a3

iPhone 6 (8.0),
iPhone 5 (10.1),
iPhone 6S (11.0)

IL2CPP,
Mono

Not reproducible with:
Android

Note:
Full crash log attached in the edit