Cache purge not working on a free plan

Hey all,

For some reason I cannot purge the cache neither via the dashboard (“purge cache” or “dev mode”), nor via the API.

The following file still shows the cached version:
/js/509.js

If you search for “cairo” in it, nothing found. But if you add a query string to it, it’s there:
/js/509.js?123

How can I fix this?
Thanks!