GCHandle value belongs to a different domain- Error in Unity playmode - music continues to play

Thanks for your patience, it looks like there is a chance that callback will be called one last time as the FMOD system releases but after the GCHandle has already been freed.

By overwriting the musicInstances user data in the OnDestroy, we can avoid this.

void OnDestroy()
{
    musicInstance.setUserData(IntPtr.Zero);
    ...

I will make sure this is added to the next release, coming at the end of the month.