Drop down box render problem

[AlpacaCCC]

Hi,
sorry to bother, I would like to ask a question about Drop down box render problem.
this is my json:

{ "type": "object", "properties": { "retryTimes": { "title": "Retry Times", "type": "number", "description": "Refers to the number of retries of this task.", "key": "retryTimes" }, "username": { "title": "Username", "type": "string", "description": "", "key": "username", "gridCloSpan": 12 }, "password": { "title": "Password", "type": "string", "description": "", "key": "password", "gridCloSpan": 12 }, "sex": { "type": "string", "description": "", "key": "sex", "gridCloSpan": 24, "enum": [ "male", "female", "unknown" ] }, "des": { "title": "Description", "type": "string", "description": "Description for user", "key": "des", "gridCloSpan": 24 } }, "required": [ "username", "password", "sex", "des" ] }

but the render outcome is like this:

why the title 'sex' is repeated?
I thought up for a long time but no result.