Certify's unbeaten record went up in smoke as she came home a disappointing fourth behind L'Amour De Ma Vie in the District One-sponsored Balanchine at Meydan.
The winner of each of her four starts as a juvenile, the Godolphin-owned filly missed her entire three-year-old campaign following a lengthy suspension due to the Mahmood al-Zarooni drugs scandal.
She made an impressive start for trainer Charlie Appleby with a dominant display in the Cape Verdi three weeks ago and was a 2-5 favourite to make it six from six in this nine-furlong Group Two.
The warning signs were there before the off as Certify appeared reluctant to enter the stalls before eventually being loaded in a blindfold. She travelled well in the hands of Mickaël Barzalona for much of the race, but was unable to quicken in the straight and was ultimately well held.
L'Amour De Ma Vie, trained in France by Pia Brandt, finished second behind Certify in the Cape Verdi, but comprehensively reversed the form, scoring by a length and three-quarters in the hands of Maxime Guyon.
Fellow French challenger Flotilla was second, building on her Cape Verdi fourth, with Eddie Lynam's Irish runner and Cape Verdi third Pearl Of Africa occupying the same position again.
Guyon said: "She ran very well last time. She finished close to Certify and tonight she won easily.
"She's improving all the time and it's my first winner in Dubai, so I'm very happy."
There was some consolation for Godolphin as Tasaday claimed the Listed Dubai Millennium Stakes in the hands of Silvestre de Sousa.
The winning rider told At The Races: "She's done it well and has come on a lot from her last run.
"I think she would appreciate some give in the ground, but she's got the class so she got away with it."