I have migrated module from Odoo 10 to Odoo 11 and when I execute a function I get and error: ValueError: Expected singleton
The goal of the function is to create a single invoice from multiple POS orders.
To reproduce issue follow this steps:
1. Create several POS orders
2. Click on "Crear factura sesion"
3. Select POS session, a client, and "Forma factura: detallada".
4. Click validate
5 Click create
This function was working fine in Odoo 10, no changes were done in migration. Also it worked on one Odoo 11 install on linux and windows, but in newers installs of Odoo 11 did not work.