The sub_filter rule '../fonts/' -> 'fonts/' was rewriting relative font paths in CSS served from /ahnenforschung/fonts/fonts.css. This caused the browser to resolve font URLs to /ahnenforschung/fonts/fonts/MaterialIcons.woff2 (double fonts/ directory). The original ../fonts/ paths resolve correctly from the subpath without rewriting. Co-Authored-By: Paperclip <noreply@paperclip.ing>