When I try to upload many photos at once using the upload utility of the "Gallery project" application, it does not upload all of them. For some of them, it gives "UNABLE_TO_LOCK_EXCEPTION" error.
The log file has the following information which does not give any clue to fix the issue. How can I fix it?
2020-07-26 21:21:55 +00:00 --- error: @todo UNABLE_TO_LOCK_EXCEPTION
#0 public_html/modules/gallery/libraries/ORM_MPTT.php(50): ORM_MPTT_Core->lock()
#1 public_html/modules/gallery/models/item.php(396): ORM_MPTT_Core->save()
#2 public_html/modules/gallery/controllers/uploader.php(192): Item_Model_Core->save()
#3 public_html/modules/gallery/controllers/uploader.php(62): Uploader_Controller->_add_item('4000', '...', 'Meenaskshi-Sark...')
#4 [internal function]: Uploader_Controller->add_photo('4000')
#5 public_html/system/core/Kohana.php(331): ReflectionMethod->invokeArgs(Object(Uploader_Controller), Array)
#6 public_html/system/core/Event.php(208): Kohana_Core::instance(NULL)
#7 public_html/application/Bootstrap.php(67): Event_Core::run('system.execute')
#8 public_html/index.php(123): require('...')
#9 {main}