Facebook Marketing API - lookalike audience creation - Can't create a duplicate lookalike

I'm making lookalike custom audiences via the Facebook API but I keep getting this error message when I try to make a second audience from the same seed:

"(#2654) Can't create a duplicate lookalike: You've already created a Lookalike Audience with the same source, country and size. Please try using a different source or different specifications."

In this case, the country and seed are the same but the ratio is different for the two audiences. When I create lookalikes to the exact same specification through adsmanager in the browser, they are created successfully.

Here are examples of the payloads I sent:

//Audience successfully created
{
  name: "LLA0%-FB | Engaged | 30 (2020-09-23) (US)",
  subtype: "LOOKALIKE",
  origin_audience_id: "123456789",
  lookalike_spec: {
    type: "reach",
    ratio: 0.05,
    allow_international_seeds: "on",
    location_spec: {
      geo_locations: { countries: ["US"] },
    },
  },
}
//Error
{
  name: "LLA20%-FB | Engaged | 30 (2020-09-23) (US)",
  subtype: "LOOKALIKE",
  origin_audience_id: "123456789", 
  lookalike_spec: {
    type: "reach",
    ratio: 0.2,
    allow_international_seeds: "on",
    location_spec: {
      geo_locations: { countries: ["US"] },
    },
  },
};

The problem with your api requests is you are specifying both type and ratio in api requests . So the ratio value is ignored by the facebook requests . https://developers.facebook.com/docs/marketing-api/audiences/guides/lookalike-audiences/#lookalike-audiences See type use either type or ratio. You should use ratio like this

{
 name: "LLA0%-FB | Engaged | 30 (2020-09-23) (US)",
 subtype: "LOOKALIKE",
 origin_audience_id: "123456789",
 lookalike_spec: {
  type: "reach",
  ratio: 0.05,
  allow_international_seeds: "on",
  location_spec: {
  geo_locations: { countries: ["US"] },
  },
},
}