Former world champion Neil Robertson suffered a 6-5 defeat to world number 71 Joe Swail in the second round of the International Championship in China.
Northern Ireland's Swail, 45, who has only reached one ranking final in his career, won three successive frames from 5-3 down to win the match.
Shaun Murphy was thrashed 6-1 by his fellow Englishman Robert Milkins.
But Ronnie O'Sullivan reached the third round with a comfortable 6-1 victory over Anthony McGill.
England's Stuart Bingham and Mark Davis and Wales' Michael White and Mark Williams also won their second round encounters to progress.
World number two Robertson, who became the eighth player in snooker history to win the Triple Crown when he added the UK Championship to his Masters and World Championship victories last December, opened with a break of 101.
He rattled off the next two frames for a 3-0 lead before Swail, who lost his professional status in 2012 before improving his form and regaining it last year, got on the board with a break of 81.
The next four frames were shared, with Robertson compiling a break of 106 to move within a frame of victory.
But Swail edged a tight ninth frame and then won the last two to set up a third-round match against China's Zhou Yuelong or England's Ricky Walden.
Englishman O'Sullivan had no such problems as he fired in three century breaks to defeat Scottish world number 40 McGill.
"I played pretty well," the five-time world champion said. "I was playing hard match snooker and didn't take many chances.
"When you play more matches that comes automatically; maybe by the time of the UK Championship or the Masters I'll have played more matches.
"I was on a roll tonight and wanted to make a century every time I came to the table."