The country finished last in the medal table, in 41st place, shared with Cape Verde.
Bangana won the bronze medal in the men's super lightweight (63kg) event.
Niambongui was disqualified in her match against Deedra Arvella Chestnut (representing Sierra Leone).
Four chess players competed: Kourakoumba Florent Desire, Koualet Bebondji Vainney Archeveque, Gamba Merveille Gloria Dan and Daher Khater Rochana.
Two athletes represented Central African Republic in judo: Hardi Malot and Loric Syssa-Magale Lagarrigue.