The week filter is not consistent, there is a 1 week offset when appling a date filter.
For example if you rund the DEMO.

Show the Expenses, and apply the daily interval, with the changes(weekly) display, the expenses are shown per week, as expected.

If you click on the 2017-W36 week, there will be no data shown, to show the 2017-W36 expenses you need to filter the date to 2017-W35.

I believe the proper week is 2017-W36 so there is a -1 week difference in the week date filter?