"Convert Lead mapping" error

Dear Sirs
With the new version of ZOHO CRM once we do a conversion from a LEAD to a CONTACT the surname is lost.
In the "Convert Lead mapping" the "Last name" value in the LEAD is not mapped to the "Last name" value in the CONTACT.

We have converted thousands of Leads into Contacts in the previous ZOHO version and everything was ok in this mapping.

Another problem is that in the "Convert Lead mapping" I can not edit the "Last name" mapping

Waiting your news, yours sincerely

Federico Castello