Maatwebsite\Excel\Validators\ValidationException: The given data was invalid in Laravel

In my Laravel-5.8 project, I am using Maatwebsites-3.1 to import excel

Imports

<?php
namespace App\Imports;
use Maatwebsite\Excel\Concerns\WithMultipleSheets;

class LeavesImport implements WithMultipleSheets
{
    public function sheets(): array
    {
        return [
            new FirstLeaveSheetImport()
        ];
    }
}

Which calles this:

class FirstLeaveSheetImport implements ToModel, WithHeadingRow, WithBatchInserts, WithValidation
{
    protected $staffid, $leavetype, $commencementdate, $resumptiondate, $reliefofficer;
    private $errors = []; // array to accumulate errors
    use Importable;

    // public function onRow(Row $row)
    public function model(array $row)
    {   
        $this->staffid = $row['staff_id'];
        $this->leavetype = $row['leave_type'];
        $this->reliefofficer = $row['relief_officer'];
        $this->commencementdate = $row['commencement_date'];

        return new HrLeaveRequest([
            'employee_id'                       => $this->getStaffId(),
            'leave_type_id'                     => $this->getLeaveType(),
            'commencement_date'                 => $this->transformDate($row['commencement_date']),
            'resumption_date'                   => $this->transformDate($row['resumption_date']),
            'no_of_days'                        => $row['leave_days'],
            'is_adjusted'                       => 1,
            'relief_officer_id'                 => $this->getReliefOfficer(),
            'reason'                            => $row['reason'] ?? '',
            'alternative_email_address'         => $row['alternative_email'] ?? '',
            'contact_phone_number'              => $row['contact_phone'] ?? '',
            'contact_address'                   => $row['contact_address'] ?? '',
            'company_id'                        => Auth::user()->company_id,
            'leave_status'                      => 4,
            'is_resumption_activated'           => 1,
            'resumption_activation_date'        => $this->transformDate($row['resumption_date']),
            'employee_code'                     => $row['staff_id'],
        ]);        

    }

    public function getStaffId(){
        if(!empty($this->staffid)){

            return HrEmployee::where('employee_code',$this->staffid)->where('company_id',Auth::user()->company_id)->pluck('id')->first();
        } else {
            return 0;
        }
    }

    public function getLeaveType(){
        if(!empty($this->leavetype) || !$this->leavetype){

            return HrLeaveType::where('leave_type_name',$this->leavetype)->where('company_id',Auth::user()->company_id)->pluck('id')->first();
        } else {
            return 0;
        }
    }    

    public function getReliefOfficer(){
        return HrEmployee::where('employee_code',$this->reliefofficer)->where('company_id',Auth::user()->company_id)->pluck('employee_code')->first();
    }

    public function getErrors()
    {
        return $this->errors;
    }

    public function rules(): array
    {
        return [
            'staff_id' => 'required|max:15',                   
            'leave_type' => 'required|max:255',
            'commencement_date' => 'required',
            'leave_days' => 'required|numeric',
            'resumption_date' => 'required',
            'relief_officer' => 'nullable|max:255',
            'reason' => 'nullable|max:255',
            'alternative_email' => 'nullable|email|max:255',
            'contact_phone' => 'nullable|phone:NG,mobile',
            'contact_address' => 'nullable|max:255',
        ];
    }  

    public function customValidationAttributes()
    {
        return [
            'staff_id'                  => 'Staff ID',
            'leave_type'                => 'Leave Type',
            'commencement_date'         => 'Commencement Date',
            'leave_days'                => 'Leave Days',
            'resumption_date'           => 'Resumption Date',
            'relief_officer'            => 'Duty Relief Officer',
            'reason'                    => 'Reason',
            'alternative_email'         => 'Alternative Email Address',
            'contact_phone'             => 'Contact Phone No.',  
            'contact_address'           => 'Contact Address',                                              
        ];
    }        

    public function validationMessages()
    {
        return [
            'staffid.*required' => "Staff ID is required",
        ];
    }

    public function transformDate($value, $format = 'Y-m-d')
    {
        try {
            return \Carbon\Carbon::instance(\PhpOffice\PhpSpreadsheet\Shared\Date::excelToDateTimeObject($value));
        } catch (\ErrorException $e) {
            return \Carbon\Carbon::createFromFormat($format, $value);
        }
    } 

    public function batchSize(): int
    {
        return 200;
    }    

    public function headingRow(): int
    {
        return 1;
    }          
}

Controller

public function import(Request $request){
    $request->validate([
        'file' => 'required|max:10000|mimes:xlsx,xls',
    ]);

  $path1 = $request->file('file')->store('temp'); 
  $path=storage_path('app').'/'.$path1;  

    try{

        Excel::import(new LeavesImport, $path);      
        
    } catch (\Maatwebsite\Excel\Validators\ValidationException $e) {
        $failures = $e->failures();
        Log::error($e);
        $errormessage = "";            

     // dd($failures);
     foreach ($failures as $failure) {
         $errormess = "";
         foreach($failure->errors() as $error)
         {
             $errormess = $errormess.$error;
         }
         $errormessage = $errormessage." ,\n At Row ".$failure->row().", ".$errormess."<br>";
     }
         // Session::flash('error', 'Excel file is not imported!');
         Session::flash('error', $errormessage);
         // return redirect()->route('leave.leave_adjustments.index');  
         return back();            
    }catch (\Illuminate\Database\QueryException $e)
    {
        $errorCode = $e->errorInfo[1];
        if($errorCode == 1062){
        Log::error($e);
        DB::rollback();
        Session::flash('error', 'You have a duplicate entry problem!');
        }
        return back();

    }
    
    Session::flash('success', 'Leave Records Imported Successfully');
    return redirect()->route('leave.leave_reviews.index_hr');         
}

When I tried t upload the excel file it shows that it was successful. But I found that no data is store in the database. So when I checked error Log, I saw these:

[2020-11-16 07:38:53] production.ERROR: Maatwebsite\Excel\Validators\ValidationException: The given data was invalid. in C:\xampp\htdocs\myapp\vendor\maatwebsite\excel\src\Validators\RowValidator.php:62
Stack trace:
#0 C:\xampp\htdocs\myapp\vendor\maatwebsite\excel\src\Imports\ModelManager.php(166): Maatwebsite\Excel\Validators\RowValidator->validate(Array, Object(App\Imports\FirstLeaveSheetImport))
#1 C:\xampp\htdocs\myapp\vendor\maatwebsite\excel\src\Imports\ModelManager.php(53): Maatwebsite\Excel\Imports\ModelManager->validateRows(Object(App\Imports\FirstLeaveSheetImport))
#2 C:\xampp\htdocs\myapp\vendor\maatwebsite\excel\src\Imports\ModelImporter.php(70): Maatwebsite\Excel\Imports\ModelManager->flush(Object(App\Imports\FirstLeaveSheetImport), true)
#3 C:\xampp\htdocs\myapp\vendor\maatwebsite\excel\src\Sheet.php(248): Maatwebsite\Excel\Imports\ModelImporter->import(Object(PhpOffice\PhpSpreadsheet\Worksheet\Worksheet), Object(App\Imports\FirstLeaveSheetImport), 2)
#4 C:\xampp\htdocs\myapp\vendor\maatwebsite\excel\src\Reader.php(111): Maatwebsite\Excel\Sheet->import(Object(App\Imports\FirstLeaveSheetImport), 2)
#5 C:\xampp\htdocs\myapp\vendor\laravel\framework\src\Illuminate\Database\Concerns\ManagesTransactions.php(29): Maatwebsite\Excel\Reader->Maatwebsite\Excel\{closure}(Object(Illuminate\Database\MySqlConnection))
#6 C:\xampp\htdocs\myapp\vendor\maatwebsite\excel\src\Transactions\DbTransactionHandler.php(30): Illuminate\Database\Connection->transaction(Object(Closure))
#7 C:\xampp\htdocs\myapp\vendor\maatwebsite\excel\src\Reader.php(115): Maatwebsite\Excel\Transactions\DbTransactionHandler->__invoke(Object(Closure))
#8 C:\xampp\htdocs\myapp\vendor\maatwebsite\excel\src\Excel.php(146): Maatwebsite\Excel\Reader->read(Object(App\Imports\LeavesImport), 'C:\xampp\htdocs...', 'Xlsx', NULL)
#9 C:\xampp\htdocs\myapp\vendor\laravel\framework\src\Illuminate\Support\Facades\Facade.php(239): Maatwebsite\Excel\Excel->import(Object(App\Imports\LeavesImport), 'C:\xampp\htdocs...')
#10 C:\xampp\htdocs\myapp\app\Http\Controllers\Leave\LeaveAdjustmentsController.php(360): Illuminate\Support\Facades\Facade::__callStatic('import', Array)
#11 [internal function]: App\Http\Controllers\Leave\LeaveAdjustmentsController->import(Object(Illuminate\Http\Request))

How do I detect and rectify the error?

Thanks