If I remember well, the impressive fall you mentioned was in the PDD (1st act second scene) in Des Grieux's room.
I found Ga´da quite convincing in the role in terms of acting even if she was not technically perfect, as usual. But in this kind of ballet, the lyricism that caracterises Ga´da's style is perhaps more important than pure technique.
Le Riche is good as usual in the role of romantic, young and passionate lover, he seems completely committed to Des Grieux's role. However, strangely, the "chemistry" of his partnership with Ga´da didn't really work (at least in my views), especially in the first act. He didn't seem concerned by his partner.Maybe you would say that this bad fall during one of the most beautiful PDD of the ballet didn't help us to get "in " the ballet...
Belarbi was quite excellent as Lescaut, his stage charisma is obvious, he is dazzling, and the PDD between Lescaut and Des Grieux (after Manon's leaving in the first act) was really good.
I will post later more details if possible but it is not easy with my poor English!