Problem:
When I create a quote in the lightning UI, the select product page alone is appearing in Classic view screen.
Solution:
For this specific scenario, the following was identified to be the problem:
We first checked the page layout of both the users, They had the same VF components "Quote Detail" and "QuoteDetailProductSelector".
Then we checked the Quote Layout of the users and found out that the "select product" button for the user who had the classic product layout view had "zqu__ProductSelect" whereas the other user had the button configured as "zqu__CpqProductSelect".
When the user changed the select product button in the layout with "zqu__CpqProductSelect". The select product page appeared correctly in Lightning UI.
