Issues with LINQ query to left join three tables

var robotNetworkData = await (
        from ni in _dbContext.RobotNetworkInterfaces
        join ns in _dbContext.RobotNetworkStatus
            on ni.RobotSerialNumber equals ns.RobotSerialNumber into nsGroup
        from ns in nsGroup.DefaultIfEmpty()
        join ss in _dbContext.RobotSystemStatus
            on ni.RobotSerialNumber equals ss.RobotSerialNumber into ssGroup
        from ss in ssGroup.DefaultIfEmpty()
        where ni.RobotSerialNumber == request.SerialNumber
        group new { ni, nsGroup, ssGroup } by new { ni, ns, ss } into g
        select new
        {
            RobotNetworkStatus = g.Key.ns,
            RobotSystemStatus = g.Key.ss,
            RobotNetworkInterfaces = g.Select(nd => nd.ni).ToList()
        }
    )
    .AsNoTracking()
    .ToListAsync();