Error 500 on GET https://kounio.gr/ :: 500 - Yet, my website still works. The error is only on console but causes all sorts of problems

My website is online and working. However it produces a 500 error every time it loads. If you run a

curl -gkvLI -b '' -H 'User-Agent: updown.io daemon 2.9' -H 'Accept: */*' -H 'Connection: Close' -H 'Accept-Language: en' -H 'Accept-Encoding: deflate, gzip, br, zstd' -m 30 --connect-timeout 10 https://kounio.gr.

The reason I ask for help for such an error is because I get no 500 error on the server side. It seems to not be an actual error and it just produces the error code while the site works and loads.

I tried bypassing cloudflare in DNS but that didn’t work. Development mode: didn’t work.
I updated plugins on wordpress, I disabled plugins on wordpress, I looked and looked and this error 500 seems to be haunting the website.

I just want to stop looking around blind and find a way to figure out where that 500 error gets produced when loading the site. And in any case, with such an error, why my site still works?

This issue, athough it does not cause any problems with the customer experience, it is really serious with services like Google Search Console and updown.io

So I need some help troubleshooting it.

It appears that the 500 error you’re experiencing is originating from your server and not Cloudflare. To troubleshoot this issue, I recommend checking your server logs for any errors or misconfigurations. Additionally, ensure that your .htaccess file is properly formatted and your WordPress installation is up-to-date. If the issue persists, contact your hosting provider for further assistance.

Ok, I hear you.

I too was suspicious about that and first suspected my server. But It’s impossible to figure out where that originates since the page loads just fine. Furthermore, there are no errors logged on any logs on my server. When I turn on wordpress error logging, I only get deprecation notices and warnings. No errors.

Also when I change the php version from 8.2 to 8.1 then to 7.4 and 7.3 I still get the same 500 error from the GET https://kounio.gr!

That’s why I turned here to ask for help!