Error message after Mollie payment

Hi,

After the Mollie payment was broken during the bank process I get the following error. Anyone know what is going on?

An uncaught Exception was encountered

Type: Omnipay\Common\Exception\InvalidRequestException
Message: The transactionReference parameter is required
Filename: /home/wesaca/facturatie.wesaca.com/vendor/omnipay/mollie/src/Message/CompletePurchaseRequest.php
Line Number: 26

Backtrace:
File: /home/wesaca/facturatie.wesaca.com/vendor/omnipay/common/src/Omnipay/Common/Message/AbstractRequest.php
Line: 610
Function: getData

File: /home/wesaca/facturatie.wesaca.com/application/modules/guest/controllers/Payment_handler.php
Line: 280
Function: send

File: /home/wesaca/facturatie.wesaca.com/application/modules/guest/controllers/Payment_handler.php
Line: 224
Function: payment_validate

File: /home/wesaca/facturatie.wesaca.com/index.php
Line: 325
Function: require_once

update 28-3-2019:
After testing again. I get this error code also after a successful payment. It looks like the redirect URL is not OK. Where can I find this? THX Freek