The Gabon international recovered from missing a sitter early on to score twice in the second half, but Aytac Sulu's last-minute equalizer denied Thomas Tuchel's side.
Pierre-Emerick Aubameyang maintained his record of scoring in every Bundesliga match this season, but Borussia Dortmund was stunned by a last-minute Darmstadt equaliser at Westfalenstadion.
Darmstadt took a surprise lead midway through the first half as Marcel Heller's stunning volley finished a fine counterattack from the visitors.
Despite missing a close-range effort to equalize before the break, Aubameyang made amends in the second period as he hooked in Marcel Ginter's low cross before putting the home side in front after Adnan Januzaj's through ball.