PDF merger is not working on live server laravel

I am using laravel package for merging pdf . This is handle function of Job which is merging in on existing file on directory but on server it skip sometimes for example it will merge 300 out of 500 files.

I think there is some thing wrong with my logic

if (File::exists($this->filepath)) {
            $pdfMerger =new  PdfMerger();
            $pdfMerger->addPDF($this->filepath, 'all');
            $bulk_pdf = public_path('bulk-pdf-consignment/manifest' . $this->manifest_id . '_.pdf');
            if (File::exists($bulk_pdf )) {
                $pdfMerger->addPDF($bulk_pdf , 'all');
            }
      
            
            $merged =   $pdfMerger->merge("file",$bulk_pdf);

Here is the exceptions it gives sometimes

Exception: Unable to find object (3, 0) at expected location. in /var/www/html/coldxlogistics/vendor/rguedes/pdfmerger/Classes/fpdi/pdf_parser.php:675

via Chebli Mohamed