ParseException when using remote ref

[Hienphamthe]

My yml hierarchy is below. In paths, I ref schema of responses to component defined in openapi_components.yml
$ref: "openapi_components.yml#/schemas/xxxxxx"
And this is where yaml.js returns error.
throw new ParseException('Unable to parse.', this.getRealCurrentLineNb() + 1, this.currentLine);
Anyone has any idea how to fix? Thanks.

openapi.yml 
openapi_paths.yml
openapi_components.yml