I am replacing a bathroom wall light with a new illuminated mirror. Sounds simple. Having switched off the relevant lighting RCD for the main bedroom and en suite on the main panel, I removed the existing light. Before fitting the new mirror light, I decided for no particular reason to check the earth to live and neutral cables with a multimeter that includes a continuity buzzer. To my surprise the buzzer sounded when connected across neutral and earth. There was no problem with the lights previously and I have made no circuit changes apart from disturbing the cables connected to the old light. Is this apparent leak because of the characteristics of an RCD and nothing to worry about?