Joomla admin intermittently losing CSS/JS across multiple sites (same server)
Hi all,
I’m running Joomla 5.4.1 on several domains on the same hosting account (HostGator). The frontend is always fine, but the administrator backend intermittently loses all styling and loads as plain text. I'm using T4BS5Blank template on all sites.
What happens
• Some days the admin looks normal
• Other times, the admin for one or more sites suddenly appears unstyled (no layout, icons, etc.)
• It can affect all Joomla sites on the account at once
• It happens in Chrome, Chrome Incognito, and Firefox, Firefox Incognito, and on different devices
When I check DevTools → Network while it’s broken, I see errors like:
• 404 /media/templates/administrator/atum/css/template.min.css
• Or sometimes 409 on the same paths
But other times, the exact same URL returns the full CSS content (Bootstrap + Atum styles), and the backend goes back to normal.
What I’ve ruled out
• Not browser cache or profiles: tested with cleared cache, new profiles, Incognito, different devices
• Not missing files: template.min.css and other assets are definitely present when the server responds
• Not a template override issue: same behavior across multiple clean Joomla installs
My suspicion
Because this is:
• intermittent
• affects multiple domains at once
• and sometimes serves the file, sometimes 404/409 for the same URL
I suspect server-side security (ModSecurity / WAF) is occasionally blocking Joomla admin CSS/JS requests under /media/templates/administrator/atum/.
What I’m asking
• Has anyone seen this kind of intermittent 404/409 on Joomla admin CSS/JS before?
• Are there known ModSecurity rules or patterns that commonly cause this with Joomla 5 admin?
• Is the usual fix to disable ModSecurity for these domains, or to whitelist certain Joomla admin paths?
Thanks in advance for any insight or example rules I can give my host.