Strange Audio Mixer Bus Issue

Hello,

I have a weird issue. Maybe you can help.

One (or some) of the busses are not played during the play mode; however, when I enable "edit in play mode" in the mixer, I start hearing those busses. Same problem occurs in the build as well.

I have this error:
/Users/builduser/buildslave/unity/build/Runtime/Audio/sound/SoundChannel.cpp(374) : Error executing result (An invalid seek position was passed to this function. )
UnityEngine.AudioSource:Play()
PlaylistController:FinishLoadingNewSong(AudioClip, AudioPlayType) (at Assets/DarkTonic/MasterAudio/Scripts/Utility/PlaylistController.cs:965)
PlaylistController:PlaySong(MusicSetting, AudioPlayType) (at Assets/DarkTonic/MasterAudio/Scripts/Utility/PlaylistController.cs:923)
PlaylistController:TriggerPlaylistClip(String) (at Assets/DarkTonic/MasterAudio/Scripts/Utility/PlaylistController.cs:682)
MasterAudio:TriggerPlaylistClip(String, String) (at Assets/DarkTonic/MasterAudio/Scripts/Singleton/MasterAudio.cs:4190)
EventSounds:PerformSingleAction(AudioEventGroup, AudioEvent, EventType, Boolean) (at Assets/DarkTonic/MasterAudio/Scripts/Events/EventSounds.cs:1096)
EventSounds:PlaySounds(AudioEventGroup, EventType) (at Assets/DarkTonic/MasterAudio/Scripts/Events/EventSounds.cs:919)
EventSounds:ReceiveEvent(String, Vector3) (at Assets/DarkTonic/MasterAudio/Scripts/Events/EventSounds.cs:1615)
MasterAudio:FireCustomEvent(String, Vector3) (at Assets/DarkTonic/MasterAudio/Scripts/Singleton/MasterAudio.cs:4584)
MasterAudioFireCustomEvent:OnEnter() (at Assets/DarkTonic/MasterAudio/PlaymakerCustomActions/MasterAudioFireCustomEvent.cs:16)
HutongGames.PlayMaker.FsmState:ActivateActions(Int32)
HutongGames.PlayMaker.FsmState:OnEnter()
HutongGames.PlayMaker.Fsm:EnterState(FsmState)
HutongGames.PlayMaker.Fsm:SwitchState(FsmState)
HutongGames.PlayMaker.Fsm:UpdateStateChanges()
HutongGames.PlayMaker.Fsm:UpdateState(FsmState)
HutongGames.PlayMaker.Fsm:Update()
PlayMakerFSM:Update()

Any ideas would be appreciated.

Thanks.