Orderlist not rendering in e-mail if customer paid with Omnikassa

Since February 2016, the Commerce Order list is suddenly not rendering anymore in the confirmation e-mail (only the e-mail!) if the customer paid with OmniKassa. Strange, because it worked properly for more than a year.

If a customer paid otherwise, the order will be sent properly (same message type, configured and sended by Rules). If I look at the message list (admin/content/messages), all the order lists are rendered correctly, even the ones paid with OmniKassa.

Could it be that the payment by OmniKassa disrupted the process of sending the order message?
Are there more people having this problem?
Could it be an issue of OmniKassa or a change on the side of the Rabobank?

I hope somebody could point me in the right direction.

Thanks in advance!