Getting {"error":"Null TypeMapping in Sql Tree"} from entity framework core using linq

I have this linq select statment and I am getting this erro {"error":"Null TypeMapping in Sql Tree"} back.

Ill put the code below but is there a way to get more information on what the issue is? If you need the entities let me know and Ill copy them.

regards

var query = from o in _orderDataDbContext.tblSellFlangeOrders
            join od in _orderDataDbContext.tblSellFlangeOrderDetails
            on (int?)o.Id equals od.SellFlangeOrderId
            join t in _orderDataDbContext.tblTypes
            on od.TypeId equals (int?)t.Id
            join l in _orderDataDbContext.VLegendeFlangeLengths
            on od.LengthId equals (int?)l.Id
            join g in _orderDataDbContext.VLegendeGrades
            on od.GradeId equals (int?)g.Id
            where o.Id == request._flangeOrderID
                        select new FlangeOrderDetailByPoCodeDto
                        {
                            SellFlangeOrderID = o.Id,
                            DetailID = od.Id,
                            Price = od.Price1000,
                            BF = od.Bf,
                            TypeID = t.Id,
                            Type = t.Inches1 + "x" + t.Inches2,
                            LengthID = l.Id,
                            Length = l.Length + "'" + l.OverLength + "\"",
                            GradeID = g.Id,
                            Grade = g.Grade
                        };