I'm betting its a conflict between the two of them, like we're gzipping it as normal, and then they are gzipping it behind us. I'm not sure who added that to your site,(might even be Cloudflare - though I am not sure about that) but it makes it hard to troubleshoot further if it can't be removed.
I found this article online:
https://wordpress.org/support/topic/cant-remove-advanced-cachephp-from-server?replies=3
which indicates its a symbolic link pointing to something else and is in the languages folder but I'm not entirely comfortable with telling you to remove stuff out of therewhen I'm not sure how your wordpress installation may have been modified by the hosting provider. I would recommend talking to them and asking first.
Hope this helps you.
tim