Hi,

This constrain is added by sql constrains in product module.

_sql_constraints = [
('barcode_uniq', 'unique(barcode)', "A barcode can only be assigned to one product !"),
]

To override the above constrains, in your custom module, inherit the product model and add the below constrains.

_sql_constraints = [
('barcode_uniq', 'CHECK(1=1)', "A barcode can only be assigned to one product !"),
]

Thanks