Error when deserializing to ProblemDetails with System.Text.Json.JsonSerializer. .Net Core 3.0

Consider the following json:

{
    "title": "SOME TITEL",
    "status": 500,
    "detail": "Some detail",
    "errors": [
        {
            "Parameter": "SOME VALUE",
            "Code": "SOME CODE",
            "Message": "SOME MESSAGE",
            "Details": "SOME EXTRA DETAILS"
        }
    ]
}

It is generated by an API response that construct a problem details like this:

var problemDetails = new ProblemDetails
{
    Status = StatusCodes.Status500InternalServerError;
    Detail = "DETAIL";
    Title = "TITLE";
};

var customClass = new CustomCalss
{
    Code = "INTERNAL_SERVER_ERROR",
    Message = "Some message",
    Details = "Extra details"
};

problemDetails.Extensions.Add(new KeyValuePair<string, object>("errors", new [] { customClass }));

When trying to deserialize the json to a problem details using System.Text.JsonSerialiser i found the following issues:

• Status, Code and Title are not deserialised to the problem details properties, they are null
• Extension data is not deserialized.

I'm testing this behavior like this:

var json = @"{
                        ""title"": ""SOME TITLE"",
                        ""status"": 500,
                        ""detail"": ""Some detail"",
                        ""errors"": [
                            {
                                ""Parameter"": null,
                                ""Code"": ""SOME CODE"",
                                ""Message"": ""SOME MESSAGE"",
                                ""Details"": ""SOME EXTRA DETAILS""
                            }
                        ]
                    }";
var result = JsonSerializer.Deserialize<ProblemDetails>(json);
Assert.NotNull(result.Detail);
Assert.NotNull(result.Title);

var customClass = Assert.IsType<CustomCalss[]>(result.Extensions["errors"]);
var error = customClass.First();
Assert.Equal("INTERNAL_SERVER_ERROR", error.Code);

Any insights?