About the issue that was occurring with MetaSounds (removed from the project in the development branch):
When referencing a MetaSound source in a blueprint that is in a Modular Game Feature with default state set to Active, the packaged game doesn’t start. The game freezes with a black screen and the last log calls are:
LogMetaSound: Error: Target interface is not registered [InterfaceVersion:UE.Source.OneShot v1.0]
LogMetaSound: Error: Target interface is not registered [InterfaceVersion:UE.Source v1.1]
LogMetaSound: Error: Target interface is not registered [InterfaceVersion:UE.OutputFormat.Stereo v1.0]
I’ve sent a bug report to Epic’ team and they confirmed the issue. You can track the status here: Unreal Engine Issues and Bug Tracker (UE-170838)
I was using MetaSound sources in some Gameplay Abilities to produce ability sound. The development branch is now using Sound Cues and have metasounds disabled to avoid this problem.
MetaSounds will be re-added to the project when Unreal’ team fix this. : )