# Crash with FMOD assertion failing during level load

**URL:** <https://qa.fmod.com/t/crash-with-fmod-assertion-failing-during-level-load/16899>\
**Category:** Unreal Engine\
**Tags:** switch\
**Created:** [March 18, 2021, 11:04am UTC](https://qa.fmod.com/t/crash-with-fmod-assertion-failing-during-level-load/16899 "2021-03-18T11:04:11Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![HarryHighDef](https://yyz2.discourse-cdn.com/flex036/user_avatar/qa.fmod.com/harryhighdef/32/666_2.png) [@HarryHighDef](https://qa.fmod.com/u/HarryHighDef)\
**Post date:** [March 18, 2021, 11:04am UTC](https://qa.fmod.com/t/crash-with-fmod-assertion-failing-during-level-load/16899/1 "2021-03-18T11:04:12Z")

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We are having an odd issue where sometimes during level load the game will crash out with the following error:

LogFMOD: Error: c:/jk/workspace/2.1\_UE4.25\_Switch/studio\_api/src/fmod\_playback\_bus.cpp(1497) - assertion: ‘instance-\>mPolyphonyEvents.isEmpty()’ failed

Is this error likely to be the cause or will it be another issue. I am opening a ticket with unreal as well and will link if its needed.

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**Author:** ![joseph](https://yyz2.discourse-cdn.com/flex036/user_avatar/qa.fmod.com/joseph/32/264_2.png) [@joseph](https://qa.fmod.com/u/joseph)\
**Post date:** [March 24, 2021, 12:22am UTC](https://qa.fmod.com/t/crash-with-fmod-assertion-failing-during-level-load/16899/2 "2021-03-24T00:22:22Z")

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That error message indicates that FMOD is trying to destroy a bus, but that there is still an event instance routed into the bus. In theory, this _should_ never happen, as any execution path that destroys a bus should end any event instances routed into it first… Could you describe how your game is handling the level transition? Especially any code that’s involved. It might help us reproduce the bug and work out why it’s happening.

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<div class="post-metadata">

**Author:** ![HarryHighDef](https://yyz2.discourse-cdn.com/flex036/user_avatar/qa.fmod.com/harryhighdef/32/666_2.png) [@HarryHighDef](https://qa.fmod.com/u/HarryHighDef)\
**Post date:** [March 24, 2021, 10:35am UTC](https://qa.fmod.com/t/crash-with-fmod-assertion-failing-during-level-load/16899/3 "2021-03-24T10:35:53Z")

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We call Open level from UGameplayStatics, with Absolute being passed in as true.

We have a sperate level for the main menu that is very light, and have the gameplay levels setup to load each sublevel in series, one after the other, to avoid issues we had before with the switch crashing. Once all the levels are loaded we load data from the save file and run some code for the level begin play.

The issue hapens when transitioning from any level to one of the gameplay levels.  
I am trying to replicate and get a much more useful log as to when the crash occurs.

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<div class="post-metadata">

**Author:** ![joseph](https://yyz2.discourse-cdn.com/flex036/user_avatar/qa.fmod.com/joseph/32/264_2.png) [@joseph](https://qa.fmod.com/u/joseph)\
**Post date:** [March 31, 2021, 12:33am UTC](https://qa.fmod.com/t/crash-with-fmod-assertion-failing-during-level-load/16899/4 "2021-03-31T00:33:32Z")

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> [@HarryHighDef](#):
>
> I am trying to replicate and get a much more useful log as to when the crash occurs.

Thank you. That will be a big help to us.

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<div class="post-metadata">

**Author:** ![HarryHighDef](https://yyz2.discourse-cdn.com/flex036/user_avatar/qa.fmod.com/harryhighdef/32/666_2.png) [@HarryHighDef](https://qa.fmod.com/u/HarryHighDef)\
**Post date:** [April 22, 2021, 12:52pm UTC](https://qa.fmod.com/t/crash-with-fmod-assertion-failing-during-level-load/16899/5 "2021-04-22T12:52:59Z")

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Managef to get another replication today but it didn’t contain any more information. I can confirm it was after it had loaded the main level and is about to load the sub levels. I’m trying to get it again with a full debugger attached.

```
[0236.59][565]LogLoad: Took 3.621551 seconds to LoadMap(/Game/Level/MainMenu/MainMenu_Master)
Entered UserExceptionHandler
Stopping HeartBeat
Stopping HitchHeartBeat
Dumping Callstack
Flushing Logs
[0266.88][565]LogFMOD: Error: c:/jk/workspace/2.1_UE4.25_Switch/studio_api/src/fmod_playback_bus.cpp(1497) - assertion: 'instance->mPolyphonyEvents.isEmpty()' failed

[0266.88][565]LogOutputDevice: Error: === Critical error: ===
[0266.88][565]LogOutputDevice: Error: 
[0266.88][565]LogOutputDevice: Error: Fatal error!
[0266.88][565]LogOutputDevice: Error: 
[0266.88][565]LogOutputDevice: Error: Unhandled Exception: InvalidDataAccess
[0266.88][565]LogOutputDevice: Error: 
[0266.88][565]LogOutputDevice: Error: [Callstack] 0x0000002C45BD3B94 (0x0000000000BCFB94) Skye.nss![Unknown]() []
[0266.88][565]LogOutputDevice: Error: [Callstack] 0x0000002C45BD3C30 (0x0000000000BCFC30) Skye.nss![Unknown]() []
[0266.88][565]LogOutputDevice: Error: [Callstack] 0x0000002C45AAB524 (0x0000000000AA7524) Skye.nss![Unknown]() []
[0266.88][565]LogOutputDevice: Error: [Callstack] 0x0000002C56E971F4 (0x00000000004A71F4) nnSdk![Unknown]() []
[0266.88][565]LogOutputDevice: Error: [Callstack] 0x0000002C56E9D7F0 (0x00000000004AD7F0) nnSdk![Unknown]() []
[0266.88][565]LogOutputDevice: Error: 
Exiting UserExceptionHandler
```