500 Server Error when search string contains diacritic characters

I am working on a WordPress site in the Danish language, and have never done a non-English language WordPress site before. I am having an odd issue with site search…

In the Nordics are a bunch of letters that are unusual as you probably know. Eg. ?, ?, & ? – otherwise known as (or at least what I’m referring to as) diacritic characters. When I type a search string into the search form on the site using any of these characters I get a 500 Internal Server Error.

The theme has already been translated and these diacritic characters seem to be displaying in the site copy just fine, so I don’t think it is an encoding issue… It seems to be more of a URL issue.

EXAMPLE: If I type ‘pr?v’ in the search form I get the 500 Error and the URL reads ‘https://resolutionmedia.dk/?s=pr?v’.
However, if I instead substitute the HTML character entity for ? in the search bar- using ‘prøv’ as the search term, I get the search results just fine and the URL reads ‘https://resolutionmedia.dk/?s=pr%26oslash%3Bv’.

I have done a bunch of searching and turned up nothing, but perhaps I am not using the right terms. As of now it seems to me like I am looking for some sort of function that will “highjack” the search term and translate any diacritic characters to their HTML equivalents before sending the search to WordPress. Any help would be greatly appreciated.