Snapping two days of gains, the Sensex at the Bombay Stock Exchange fell 71 points, or 0.4 percent, to 17,657, on profit-booking by investors,on Thursday. The Sensex had gained 171 points in the last two trading sessions. The Nifty at the National Stock Exchange lost 17 points, or 0.3 percent, to 5,363. Stock markets in Japan, China, Hong Kong, South Korea and Singapore ended mixed.