Steps to reproduce the issue

Open the page in chrome

Expected result

every custom.css edit to function

Actual result

no custom css function

System information (as much as possible)

Template: Purity III from Joomlart
Joomla version: Latest

Additional comments

I found this thread: #14220
Which adress my issue to a toe. How ever it was closed so I'm opening a new one. My issue is the same. Purity III and other joomlart templates run with a Custom.css option which should work to override any Css on the site. In Firefox it works fine, but in chrome and Edge the stylesheet is not loading properly. What do I do?