Can't see your screen shot. My browser is acting a bit wonky so it may be my browser that's causing the problem here.
Some people use the same table for invoices and quotes. They add a field that labels a given record as one or the other and then they use a duplicate record script when they want to use a Quote record to start a new Invoice Record.
Don't see how creating a new quote record, no matter what method you use, could affect the records in the products table as this should be a separate table, but then I might understand if I could see your tables and relationships.