[مغلق] I get error 500 when I order on one language, on other it works

Background of the issue:
I am trying to buy a product in the Serbian language on my site الرابط المخفي. When I attempt this, I encounter an error. This is the URL example of the product: الرابط المخفي. I am not following any documentation.

Symptoms:
I get a 500 Internal Server Error when trying to order a product in Serbian. The error message is: jquery.min.js?ver=3.7.1:2 POST الرابط المخفي 500 (Internal Server Error).

Questions:
Why do I get a 500 error when ordering in Serbian?
How can I resolve the 500 Internal Server Error on my site?