Error in sale_complaint action


In sale_complaint action “Create sale return” with some lines of the sale added, I get the cryptic error message
The value of the field "Product" on "Sale Line" is not valid according to its domain.
when I click Process. Version 5.0.17.

This is probably because some products are no more salable. I’m wondering if we should not allow non salable product for return (negative quantity).