Hello Odoo Community

   I have created two custom fields: one to show related sale orders in the purchase orders form and list view, and the other to show the opposite. What I did is as following: field name: x_purchase;  field type: many2many; related model:  purchase.order; relation table:  x_purchase_order_sale_order_rel; column 1:  sale_order_id; column 2:  purchase_order_id. I then added the x_purchase field to Sale model-->list view and form view and vice verca to the purchase model. 

So far, showing sale orders in the purchase module works perfectly. However, I received error message when trying to select past purchase orders in the sale module. The error message implicates that there is no client_order_ref under purchase module. How can I fix this? Should I make a custom addon? If so, what code should I write?

Additionally, I have an inherited views of delivery status, which shows up under purchase->sale order, but not sale->purchase order, please let me know how I can fix that too. 

Many thanks!