Sorting not working with IMongoQueryable

Hi All,

We use MongoDB as our application database integrated through .NET Core 6.0.The C# driver version is 2.19.0.
We are facing an issue with sorting where we need to sort by a field and put a specific value on top.
We have a C# class which is as follows.

public class CaseShortInfo
    public IList<AdditionalAttributesNst> AdditionalData { get; set; } = new 
    public string BatchNumber { get; set; }
    public string CaseName { get; set; }
    public string CaseNumber { get; set; }
    public string CaseOriginName { get; set; }
    public IList<CountryEntity> CountryList { get; set; } = new List<CountryEntity>();
    public bool External { get; set; }
    public IList<IdNameNst> GeneralIndicators { get; set; } = new List<IdNameNst>();
    public string Id { get; set; }
    public IList<IdNameNst> IdentificationResult { get; set; } = new List<IdNameNst>();
    public IList<IdNameNst> Indicators { get; set; } = new List<IdNameNst>();
    public int? OrderNo { get; set; }
    public string PrimaryPartyName { get; set; }
    public string ProductId { get; set; }
    public string ProductNumber { get; set; }
    public int Quantity { get; set; }
    public int? QuantitySeized { get; set; }
    public IList<string> Tags { get; set; } = new List<string>();

We have a function which returns IMongoQueryable

var queryable = await GetCaseShortInfoQueryable();

We want to sort it so that values matching a specific product are arranged at the top with this LINQ query.

queryable = queryable.OrderByDescending(x => x.ProductId == "1234").ThenBy(x => x.productId);

But somehow the objects with Product Id 1234 are grouped together but get listed in between and never get listed at the top.

When we try the same with any C# IQueryable, it works fine.

So would like to know the reason for this behavior.

Thanks in advance