DynamicParameters retrieval failing with NullReferenceException after moving to Microsoft.Data.SqlClient

We encountered an issue retrieving DynamicParameters using the Get method after the QueryAsync method was finished. 
The stored procedure always returns the parameters we are looking for. Most of the calls are working fine, but still, the issue appears for less than 1% of cases with the next call stack:

System.NullReferenceException: Object reference not set to an instance of an object.  
at Dapper.DynamicParameters.Get[T](String name) in /_/Dapper/DynamicParameters.cs:line 329

This issue has been started right after moving from System.Data.SqlClient to Microsoft.Data.SqlClient

Code example:

using (var connection = new SqlConnection(_connectionString))
{
    await _asyncRetryPolicy.ExecuteAsync(() => connection.OpenAsync());

    DynamicParameters queryParameters = new DynamicParameters();
    queryParameters.Add(name: ERROR_CODE_PARAMETER_NAME, value: null, dbType: DbType.Int32, direction: ParameterDirection.Output);  
    queryParameters.Add(name: ERROR_MESSAGE_PARAMETER_NAME, value: "Unknown error", dbType: DbType.AnsiString, direction: ParameterDirection.Output, size: ERROR_MESSAGE_LEN);  

    var result = await connection.QueryAsync<T>(storedProcedureName, queryParameters, commandType: CommandType.StoredProcedure, commandTimeout: commandTimeout);

    int errorCode = queryParameters.Get<int>(ERROR_CODE_PARAMETER_NAME); // NullReference here
}

Could you please help us troubleshoot this issue?
Thank you.

Additional context
Microsoft.Data.SqlClient v.5.2.0
Dapper v.2.0.123

Start at DynamicParameters.cs line 329 and trace how QueryAsync populates output parameters before Get is called. Reproduce the supplied stored-procedure example with Microsoft.Data.SqlClient 5.2.0 and Dapper 2.0.123; done means identifying the intermittent null path and resolving or clearly documenting the cause.