Currently running 1.17.1 and have been using OSTicket for over a year.
I have always had a Business Hours schedule set up that is basically 9am to 5pm Monday to Friday to help the SLA feature to calculate overdue times accurately.
However for the first time I've now tried to make use of custom Holiday date ranges to further refine our open hours so that SLA's can be calculated properly across extended holiday periods. (In other words, so the system doesn't bug me over extended holiday periods when we're closed. 🙂 )
However I only seem to be able to add a single date range before I get the warning "Other entries already exists":

In the screenshot I have an initial range of dates from 16-20 October 2023 (daily repeating, all day) which saved correctly, however when I try to add a second range of dates from 25-29 December 2023 (also daily repeating, all day) I get this error and cannot save the date range.
The user interface seems to suggest that a holiday schedule can consist of multiple dates or multiple date ranges, and the default sample "US holidays" has multiple dates in it.
Anyone have any ideas ? I see one similar query on here four years ago with the same problem but the only response was "try the latest RC candidate" with no further follow up. Obviously we are several versions past that now but the same issue still seems to be there.