Emma Raducanu again failed to take three match points as she was beaten 6-3 6-7 (9-11) 6-0 by Jessica Pegula in a hard-fought last-32 tie at the China Open.
The British number one, who lost to Barbora Krejcikova in similar fashion earlier this month, faded in a match that lasted two hours and 21 minutes.
Meanwhile, fellow Briton Sonay Kartal advanced to the round of 16 after beating Maya Joint in Beijing.
Raducanu, ranked 32 in the world, took the first set against world number seven Pegula before both players wrestled for control in the second - the usually composed American giving a shout of frustration and throwing her racquet to the floor in the fifth game.