I retried and in fact it's strange. Sometime it works but doesn't show all the results, sometimes it just doesn't work. Examples: I have approximatively 10 contact with firstname "vincent" but when I write Vincent it goes directly to fallback after I write the first letter "v". In another hand I also have 10+ contact with firstname "françois" and when I write it looks like it works but just show me one result!?!? Strange, strange, ...