Steps to reproduce the issue

Since I installed joomla 3.8.0 items are inserted twice in the database. I tried several methods and nothing works:

// method 1
$db = JFactory::getDbo();
$query = $db->getQuery(true);
$profile = new stdClass();
$profile->modif_id = $modif_id;
$profile->product_id= $ajout_prod_id;
$profile->nombre= $ajout_prod_number;
$result = $db->insertObject('mytable', $profile);

//method 2
$db = JFactory::getDbo();
$query = $db->getQuery(true);
$query = "INSERT INTO mytable (modif_id, product_id, nombre) VALUES ('".$modif_id."', '".$ajout_prod_id."', '".$ajout_prod_number."')";
$db->setQuery($query);
$db->execute($query);

Expected result

Item inserted in the database only once

Actual result

Item inserted twice in the database

System information (as much as possible)

Joomla 3.8.0
Regular Labs - Sourcerer 7.1.9

Additional comments

Everything was working well before the 3.8.0 update. It has been stable for years.