Does your configuration work correctly when files are proxied and if
you call for a file_fragment before the whole file is cached?
(Example, if you hit /file.mp4?start=10&end=20 and the cache is empty)
Also, I noticed in my case, HEAD requests are set to the origin
server, not using the cache file. (Regardless of the file being in
cache or not)
In my case, I'm using 1.4.23 with modcache v1.8.0...