Error with CI 3.1.2

New error popping up when upgraded to CI 3.1.2.

Code:

Error Number: 1064

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'THEN '1109' ELSE `wopart_id` END, `qty` = CASE WHEN `wopart_id` = THEN '2' ELS' at line 2

UPDATE `WOPARTS` SET `wopart_id` = CASE WHEN `wopart_id` = THEN '1109' ELSE `wopart_id` END, `qty` = CASE WHEN `wopart_id` = THEN '2' ELSE `qty` END, `price` = CASE WHEN `wopart_id` = THEN '59.40' ELSE `price` END WHERE `wopart_id` IN()

Filename: models/Transaction_model.php

Line Number: 131

This is the section of Transaction_model in question. Nothing in the model changed but somehow the insert_batch function is not working right with the latest update. Any ideas?

Code:

$this->load->model('parts_model');
        if($this->input->post('woPartsEdit') ){
            $woPartsEdit = $this->input->post('woPartsEdit');
            if(isset($woPartsEdit['wopart_id'])){
                $update_data = array();
                foreach($woPartsEdit['wopart_id'] as $key => $val){
                    if(isset($woPartsEdit['qty'][$key]) && isset($woPartsEdit['price'][$key]) ){
                        $update = array();
                        $update['wopart_id'] = $val;
                        $update['qty'] = $woPartsEdit['qty'][$key];
                        $update['price'] = $woPartsEdit['price'][$key];
                        $update_data[] = $update;
                    }
                }
                if(count($update_data) > 0) $this->db->update_batch('WOPARTS', $update_data, 'wopart_id');
            }
        }