Notification Callback locking transient.

[Icarleug]

If a customer fails the payment and tries again, and the rety also fails, the transient return and locks out the transaction until the transient times out.

In class-wc-gateway-mondido-hw.php, function notification_callback(), rows 510+

// Use transient to prevent multiple requests
if ( get_transient( 'mondido_transaction_' . $transaction_id . $status ) !== false ) {
   $this->log( "[IPN] Payment confirmation rejected. Transaction ID: {$transaction_id}. Status: {$status}" );
   header( sprintf( '%s %s %s', 'HTTP/1.1', '200', 'OK' ), TRUE, '200' );
   echo "[IPN] Payment confirmation rejected. Transaction ID: {$transaction_id}. Status: {$status}";
   return;
}

Since the use of a return instead of a throw the transaction never unlocks.
Suggestion:

Add an unlock before the return.

// Unlock order processing
$this->unlock_order( $data['payment_ref'] );