HTTP_RESPONSE not fired every time when OneConnect enabled

I write an iRule to let F5 to insert "Cache-Control" header when it sees 3xx/4xx/5xx response:

 
 when HTTP_RESPONSE { 
   if {[HTTP::status] >= 300 and 
       not [HTTP::header exists "Cache-Control"]} { 
     HTTP::header insert "Cache-Control" "must-revalidate, no-cache, no-store" 
   } 
 } 
 

But I notice that, when OneConnect enabled, not every 4xx request will be inserted "Cache-Control".

I also tried to simplify the problem to:

 
 when HTTP_RESPONSE { 
   HTTP::header insert "Cache-Control" "must-revalidate, no-cache, no-store" 
 } 
 

In theory, I would see Cache-Control for every request, but it didn't. I only see 30~35 reqs for 100 requests.

System is BIG-IP 9.4.7 Build 330.0 Hotfix HF2.