The truth is that I had to transfer the client from Turbotax to Proseries and the following error happens during the transfer. If there is an entry in Turbotax on Sch A line 8(a) ("Home mortgage interest reported to you on Form 1098"), when the return is transferred from Turbotax to Proseries, Proseries erroneously transfers the amount of interest on the mortgage on Sch A twice: on line 8(a) which is correct and then the same amount on line 8(b) ("Home mortgage interest not reported to you on Form 1098).

So, in fact it was not even my mistake but an error in Proseries which still has to be fixed. I had other clients with similar transfers and I had to manually correct the situation but for this client I missed it.