Special (non-latin) alphabet letters in URLs
There is a bug with the special alphabet letters, ONLY for Product Detail Pages.
When viewing a product in Danish or Swedish language, which has special (non-latin) alphabet letters in the URL, and then switch language (from Danish to Swedish or the other way around) the new page is a 500 server error page!
This is a big drawback, as some of our customers (that convert) change the language of their landing page. I can see that in Google Analytics reports; Acquisition -> All traffic -> Channels -> Referral
This doesn't happen for flexi pages or product list pages. This means that it is not the special letters that create the problem, but the PDPs.
Each page has its equivalent pages in different languages. So, the PDPs should always direct to the same page, but in different language, when switching languages.
Florian Ammon commented
The problem may be related to the Google Bot crawling web pages. We got a lot of error messages in our Google Search Console because it wasn't possible for the bot to crawl them. If I do remove following characters in my url "%25c3%25a4" and and replace them with the umlaut "ä" as supposed, the link is working. Usually the product number at the end of an URL does count only. But these url encoded characters cause en server error.