New signing Tony Andreu contributed two goals, but they remain seven points behind leaders Hibs and needed to survive a nervy final half-hour with ten men following a red card for defender Paul Dixon.
The first part of Dunfermline’s penalty trilogy was played out in the ninth minute after United defender William Edjenguele pushed Lee Ashcroft. Gavin Reilly’s spot kick was cleanly-struck but at a convenient height for Bell to claw it away.
Striker Simon Murray’s crisply-taken opener compounded the home team’s misery in the 20th minute, and further embarrassment was just around the corner when Nicky Clark repeated Reilly’s miss after being tripped by Frank Van Der Struijk.
The situation became farcical on the half-hour mark as Paul McMullan produced a carbon copy of Reilly and Clark’s failed attempts, allowing Bell to pull off a third penalty save.
The visitors doubled their lead barely 60 seconds into the second period when Andreu’s 18-yard drive was blocked by keeper David Hutton, but vicious spin took the over the goal-line.
Dunfermline needed an instant response and Michael Paton provided it when he latched onto Clark’s deflected shot to score. They were handed another lifeline in the 58th minute when Dixon was red-carded for a second bookable offence, but Andreu made it 3-1 at the death.