There may be troubles with the fast write/read for the cache files on your server's hard drive. For a quick check, you may switch the cache engine from the Files to Memcache variant in the Studio->Settings->Cache are (if you have the ready Memache on your server).
We already use Memcache as a cache engine. Nearly all files of the 'cache' folder are stored there. However, this has no effect on the 'cache_public' folder. CSS, LESS and JS files are still stored in this folder.
