Hi Neil, we've seen your post and want to help. But in Tableau 'drill-down' and 'sorting issues' & 'table calculations' are extremely contingent/dependent on many different factors -- things that can't be discerned from jpg's. If you can't post a mock-up of your data (scrambled of course) in a packaged workbook (twbx) I'm not sure you're going to get a bite on this one.
I have the same issue. Please point me to an idea or existing answer if available.
I have a year field that is sorted descending but when drill down to the quarters, they are sorted ascending. This gives a graph or chart that is out of order. I would like the sort order to remain as descending as I drill down from year to quarter to month.