Doubt in Query logic in Laravel 10

Dear Friends, I have a form structure as shown below

I am trying to implement a logic while adding new entry with unique short_name as

 public function GetPenaltyStatus(Request $request)
    {
        $start_date = $request->start_date;
        $end_date = $request->end_date;
        $short_name = $request->short_name;
        $flag = 0; // if flag is 0 can add new entry if 1 did not allow
        $startDate1 = $start_date;
        $endDate1 = $start_date;
        $startDate2 = $end_date;
        $endDate2 = $end_date;
        if ($end_date) {
            $penalty = PenaltyMaster::where('short_name', $short_name)
                ->where(function ($query) use ($startDate1, $endDate1, $startDate2, $endDate2) {
                    $query->where(function ($subQuery) use ($startDate1, $endDate1) {
                        $subQuery->where('start_date', '<=', $startDate1)
                            ->where('end_date', '>=', $endDate1);
                    })->orWhere(function ($subQuery) use ($startDate2, $endDate2) {
                        $subQuery->where('start_date', '<=', $startDate2)
                            ->where('end_date', '>=', $endDate2);
                    });
                })
                ->exists(); // one condition
            if ($penalty) {
                $flag = 1;
            }
           
        }  
            $penaltyRem = PenaltyMaster::where('short_name', $short_name)
            ->whereNull('end_date')
            ->exists();
            if ($penaltyRem) {
                $flag = 1;
            }
        return response()->json(['flag' => $flag]);
    }

The above ajax logic checks if flag is 0 can add new entry if 1 did not allow.

But above query logic is not working . In my table has short_name as "D" has start_date 03/05/2024 and end_date 11/05/2024 but when I try to add a new short_name with name D with start_date 17-05-2024 and end_date as 19-05-2024 blocks and return 1... But in my case I need to add that entry to table .

My penalty_master table structure as

CREATE TABLE `penalty_master` (
  `id` int(11) NOT NULL,
  `penalty_name` varchar(255) NOT NULL,
  `short_name` varchar(50) NOT NULL,
  `status` varchar(3) NOT NULL DEFAULT '1',
  `penalty_rate` float,
  `start_date` date DEFAULT NULL,
  `end_date` date DEFAULT NULL,
  `created_at` datetime NOT NULL DEFAULT current_timestamp(),
  `updated_at` datetime NOT NULL DEFAULT current_timestamp()
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_general_ci;

ALTER TABLE `penalty_master`
  ADD PRIMARY KEY (`id`);

--
-- AUTO_INCREMENT for dumped tables
--

--
-- AUTO_INCREMENT for table `penalty_master`
--
ALTER TABLE `penalty_master`
  MODIFY `id` int(11) NOT NULL AUTO_INCREMENT;

In this form , end date field is not MANDATORY. If for an entry that is blank , don't allow to entry that short code in table once more. In start_date , end_date fields entry is greater than current one can allow to save.

Any body please correct my code for a good logic

Thanks

Anes P A