Marketpress Mollie checkout is not working


I am busy creating a website to sell tickets, but also products. To create this I had to buy another (external) plugin for the events since Mollie is not supported by your events plugin.

We went for Tickera and it works really nice. However, it causes a problem (500 error) with Marketpress when paying through the Mollie gateway. Tickera still works with Mollie, but not with Marketpress...

It goes well untill you "pay" the product and a confirmation is send back to the website. Then it shows an internal server error.

Hope you know how to solve this or have a workaround.
(I tried building event tickets with marketpress in combination with events, but that didnt get me where i wanted)

Kind regards,