Codeigniter 3.x and MariaDB transactions rollback not working for all records

This is driving me crazy for days.

When I build query and insert in some of the tables it is commiting automatically, while other times it doesnt.

Checked all threads but nothing works. I have this code:

$this->db->trans_begin();

        $q1 = $this->db->insert('log_query_actions', array('created_time' => '11:11:11'));
        $q2 = $this->db->insert("db_sales", array('store_id' => '1'));
        $q3 = $this->db->insert("db_sales", array('store_id' => '2'));
        $q4 = $this->db->insert('log_query_actions', array('created_time' => '22:22:22'));
        $q5 = $this->db->insert("db_sales", array('store_id' => '3'));
        $q6 = $this->db->insert('log_query_actions', array('created_time' => '33:33:33'));

        $this->db->trans_rollback();
After execution, in Database I can see the first 2 inserts for each table. The 3-rd insert in each table is successfully rolled back: 
NOT ROOLLEDBACK $q1 
NOT ROOLLEDBACK $q2 
NOT ROOLLEDBACK $q3 
NOT ROOLLEDBACK $q4 
ROOLLEDBACK $q5 
ROOLLEDBACK $q6

If I try something else, like:

                    $this->db->trans_begin();

        $q1 = $this->db->insert('log_query_actions', array('created_time' => '11:11:11'));
        $q4 = $this->db->insert('log_query_actions', array('created_time' => '22:22:22'));
        $q6 = $this->db->insert('log_query_actions', array('created_time' => '33:33:33'));
        $q2 = $this->db->insert("db_sales", array('store_id' => '1'));
        $q3 = $this->db->insert("db_sales", array('store_id' => '2'));
        $q5 = $this->db->insert("db_sales", array('store_id' => '3'));

        $this->db->trans_rollback();
Then ONLY $q5 IS ROLLEDBACK. Everything else is in the table.

AND HERE COMES THE INTERESTING PART:

                    $this->db->trans_begin();

        $q2 = $this->db->insert("db_sales", array('store_id' => '1'));
        $q3 = $this->db->insert("db_sales", array('store_id' => '2'));
        $q5 = $this->db->insert("db_sales", array('store_id' => '3'));
        $q1 = $this->db->insert('log_query_actions', array('created_time' => '11:11:11'));
        $q4 = $this->db->insert('log_query_actions', array('created_time' => '22:22:22'));
        $q6 = $this->db->insert('log_query_actions', array('created_time' => '33:33:33'));

        $this->db->trans_rollback();
In this case EVERYTHING IS ROLLEDBACK except $q2 and $q3.
What is happening with db_sales table that is commiting the changes? There are no internal relations, and Engine is INNODB not MyISAM