Gorilla silverbacks at Port Lympne killed male diana and colobus monkeys during the 1990s after attempted mixings.
The male Gorilla 'Jomie'( Djoum x Lomie, owned by ZSL) killed and partially ate a Colobus Monkey in the old 'tower' ex Chimpanzee age at Port Lympne. He was later sent to London Zoo but died two years later from Hepatitis B. I can only suspect he might have got it from eating the Colobus monkey, as no other cases have been reported of other Gorillas there so affected.
Most places that have kept Monkeys with Gorillas seem to suffer accidents to one or more Monkeys eventually, and then give it up as you outlined. Bristol's with De Brazza's seemed to work initially but then just stopped.
One other I know of is GaiaPark where they have(or had) Black Mangabeys with Gorillas.