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Here is the scenario:
The view called "reports" has a lot of stuff defined in its master, including fields, filters, contextual filters and relationships.
There are 3 displays in that view:
1+2) A page and a related export for monthly reports
3) A page for daily reports
The displays 1 and 2 are using all the settings from master without any changes.
The display 3 modifies the filters and the contextual filters.
This way, the maintenance of that views is kept as little as possible and everything apart from one thing works really well.
That one thing is that there are no values in the calculated rows at the bottom of the display 3 (daily reports). That's the display that has different filters from the master. After several hours of debugging I found out that by cloning the view in execute_summary_view() there are still the arguments from the master taken forward and they brake the query of that display. Hence, we never get back any values from that query.
To fix this in my case, I removed all filter from the master of my view and moved them into each individual display. Now, also the display 3 is working correctly. Just the downside that when I'm now changing filter definitions I will have to do that more than once potentially.