Problem trying to print a pdf of an Invoice

Hello all
We are using SuiteCRM 7.9.8 to produce a PDF that will print the invoice of an AOS_Invoice record.

We are using the PDF-Templates module and selecting the sample template that is already present in SuiteCRM, however the issue we are finding is that, even in the sample template, the Item lines and the Group lines they are not being printed with the actual values.

I mean the header (name of the customer, address…) work fine, but when we want a table with the list of items bought in the AOS_Invoice record and the total ammount of the Invoice… we are only able to see the “name” of the fields of the module (like $aos_products_quotes_products_aty), but never their value.

For example, when the invoice has 5 lines, instead of getting a table with all the lines and their values, we get this. (see attachement)

Is this a bug, or are we missing a configuration we have pending?

Thanks a lot!!