FDS Date Hierarchy Display & Sorting

Hi Team,
I'm trying to get a hierarchy configured in FDS and have a couple of issues.
When displaying the data in a form, the date (day) column shows without formatting to the correct date format. Only certain dates are formatted correctly. All data is in the correct format of 'YYYY-MM-DD'. This display issue does not occur for all records.
This is causing the sort order of the data to behave erratically due to the display of the data not using the assigned format.
The attached screenshots show the FDS Mapping, field filter selection and the display.
Slice is defined as
{"rows":[{"uniqueName":"Date Price"}],"columns":[{"uniqueName":"[Measures]"}],"measures":[{"uniqueName":"RB","aggregation":"count","grandTotalCaption":"Book"}],"drills":{"rows":[{"tuple":["date price.[2019]"]}]}}
Mapping is as below for the date hierarchy.
"DPyr":{"type":"number","hierarchy":"Date Price","dimensionUniqueName":"Dates","caption":"Year"},"DPmth":{"type":"string","hierarchy":"Date Price","dimensionUniqueName":"Dates","caption":"Month","parent":"DPyr"},"DP":{"type":"date string","hierarchy":"Date Price","dimensionUniqueName":"Dates","caption":"Day","parent":"DPmth"}