Help: order details turn into text page after status change

[Wicked-Shop]

Hi,

 

We are currently in the testing our shop and so far we have been very satisfied. A few things still have to adjusted and/or fixed. The last test order we made on April 17th, after that we did not change a lot. We only inserted Slider-HTML texts within the module for that but nothing else. We tried to install a module which enables modified invoices (comes with templates for that which can be edited then in prestashop) but it did an override so our other module to attach Terms & Conditions to confirmation emails did not work, so we deinstalled the template module again. Also we kept the T&C email attachment module deinstalled for now while testing. 

 

So, today we did some further test orders again and then something happens in the backend under "Orders". When we tried to switch the order status the page simply turns into a blank html page with only text and a few icons. All other parts of the backend remain intact. We deactivated the modules mentioned above and also re-activated them, but it did not fix the problem.

 

Our Prestashop version is: 1.6.1.18 , we are running the installation on a STRATO webspace (shared webspace) plan. 

 

Here are screenshots to show the issue.

 

Before:

 

After:

 

Any help would be appreciated, as we cannot figure the problem solution!

 

Thank you!