Hi Nicolas,
Thanks for the reply.
1. ok, that was indeed the case (I can see much much more customisations than I have made...) SO now I removed the customisation for the payment block (had the same problem) and the shipping block. Only thing is that there is one payment method that should only be available for one specific shipping method. That seems to be broken now. Anyway, it is possible now to finish the order, that was the most important thing, but if this could be working again it would be great.
2. I can customise the email template, it will work. but whenever I use the 'per status override' the things like {TXT:HI_CUSTOMER} will result in 'Hello %s' instead of 'Hello John'. I've added a screenshot. The ordered item is also missing, if I don't use the 'per status override' the ordered item will show up correctly.