Date Fields Not Displaying In Rows/Columns - Compact Form - Custom DataSource API

We are using the Custom Data Source API to retrieve data into Flexmonster. We are seeing an issue when our default layout form is Compact/Classic.

Given a Date field in the Rows/Columns with a simple aggregation in Values, no rows are returned.  However, the grand total is correct and drill-through shows that all data was returned correctly.  Both request and response seem correct.  

With the same query, when we switch to Flat mode, all data displays as expected.  Then, when we switch back to Compact mode, the rows display as expected.

When we run the same query with string/number data types in Rows/Columns everything works as expected.

Data being returned is the same for all modes.  There is no difference in the response data in compact mode before and after the switch to flat mode.

Only minor changes were made to the sample .Net Core code provided on the Flexmonster site: https://github.com/flexmonster/api-data-source/tree/master/server-dotnetcore

We are using Flexmonster version 2.9.44.  We tested with the latest version 2.9.104, and got the same results.  

Thanks,

Rob (using Kunal's account)