Hi miguel1258 ,
Apologies for the late response. We have had a long holiday weekend the last week.
Yes, we give support here.
We tried to reproduce your issue in a local installation. It worked as expected.
Please answer the next questions:
Does the problem repeat when you create a new PO with the same product? What's the difference between this product and the products with quantities added correctly? Does the error happen with any other product?