I consulted our QA for some explanation with respect to the behaviour of the solution, according to them the core issue here is, that the search is being sorted by a column (Customer) containing multiple identical values. This causes that the results might be in different order each time the search is executed, which can lead to a row being two pages, but does not duplicate them (note that the total number of rows is the same as in exported file). According to them, the behavior is by design.