Crash with FMOD assertion failing during level load

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.

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.

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.

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