The solution involves some C++.
MediaSoundWave.h :
Under “virtual void Serialize( FArchive& Ar ) override;”, add this declaration:
virtual void PostLoad() override;
In MediaSoundWave.cpp, add the function:
void UMediaSoundWave::PostLoad()
{
InitializeTrack();
Super::PostLoad();
}
And modifiy also HandleMediaPlayerMediaChanged, at the end of the file:
void UMediaSoundWave::HandleMediaPlayerMediaChanged()
{
PostLoad();
}
Hope this help,