Steps
Leads, convert to opportunity -->Conversion Action: Convert to opportunity -> Select : Sales person, Select: sales team 

Customer: select -->Link to an existing customer

Actual Behavior:

Odoo change the selection to MERGE WITH EXISTING OPPORTUNITIES

have to reselect: Convert to opportunity

Customer: Select any customer

and Odoo change again selection to: MERGE WITH EXISTING OPPORTUNITIES

have to reselect: Convert to opportunity

Expected behavior:             

Don't change selection made by user.