After Natalia hears interference in her hearing aid, she realizes that Eric is wearing a wire. She then closes the door to her lab so that she can talk privately with Eric being wired and about missing evidence at the lab. But the 'walls' of her lab are made up of horizontal glass panes that do nothing to block sound. So anyone standing in the hall or walking by would have been able to hear their entire 'secret' conversation.
Supposedly the gold was shaped like motorbikes and then painted in order to pass through customs. It would have taken a lot of resources and time and people to do that. A bit much for a two woman crew in a couple of days.