On certain version of iOS and Safari users get NSPOSIXErrorDomain:100 errors

On certain versions of iOS and Safari some users visiting our website jetclean.dk gets NSPOSIXErrorDomain:100 errors.

To reproduce this:

• Load the website on a browser with issue .
• Go to a second page.
• Visit the homepage back by clicking on the logo or link to the homepage.
• Do this a few times if needed.

Known browsers with issues:

• Safari Browser 11.0.2 and above
• Chrome for iOS - Version 69.0.3497.105
• Safari - Version 12.0 (14606.1.36.1.9)

This is only happening on getgrav front end - while the admin is working fine.

Please advise

I can't reproduce the issues in same versions you listed :)
Have you tried to clear cookies as suggested here?
https://discussions.apple.com/thread/7612610