List view grouped by type “Number” then by type “Text” does not expand to show entries in SharePoint Online

List view is grouped by field “Created year” of type “Number” and then by field “Created month” of type “Text” does not show entries while trying to expand the grouping. Both are calculated columns and return Number and Text respectively.

I have also tried by returning Date from “Created year” and also Date from “Created month” but it still does not let item entries expand

Column: Created year settings: enter image description here

Column: Created month settings: enter image description here

View group by settings: enter image description here

List view does NOT expand values: enter image description here

Where am i wrong?