When creating a lead from an existing contact and account, all data from contact and the account is not getting mapped. OOB Mapping is not able to map all the details from contact and account as of now. OOB Mapping is working in some cases and in some cases we have to use customization like JavaScript . As our business wants to keep low customization. We want to map More fields using out of the Box Mapping.

Example: A customization field named European Vat ID is not getting mapped OOB in spite of being present in both Account and Lead.