As of my investigation, Look like this problem just occure when cloudflare don’t have cached on that file. So Cloudflare must load that file from origin server. after load completed Cloudflare does not sent that result to client.
After second refresh that file can responsed (My view is cloudflare already cached that it from the first request)
So, As I understand this this is the issue on cloudflare site.
Note: This ploblem got only the “proxied” on.
How to slove this issue, please advice.