Solution : https://service.sap.com/sap/support/notes/969558 (SAP Service marketplace login required)
Key words :
terms bupa_select bua_but021_select_with_adrkind adress_td_xpra bupa_td_partner_switch reason, system supports gradual conversion, gradual conversion process, relevant tables but020, parnters remain unconverted, system moves, business partners, address data, programming error, solution apply