iRule - unexpected behavior

Hello Community,

I have recently experienced an unexpected behavior from an iRule, where the http responses were intermittent and failure detected on the last event in the iRule HTTP_RESPONSE_RELEASE.

We have noticed the odd behaviour started when the log destination pool members failed to respond to health-check monitor (server down).

Below is a snippt of the iRule event where the failure observed.

when HTTP_RESPONSE_RELEASE {
    # figure out the final duration and add it to the IPFIX log
    set stop [expr {[clock click -milliseconds] - $start}]
    IPFIX::msg set $rule1_msg1 flowDurationMilliseconds $stop
    
    # send the IPFIX log
    IPFIX::destination send $static::http_rule1_dest $rule1_msg1
  } 

 I'm questioning two things:

1. Why the failure was intermittent and havent affeted all responses?
2. Why the pool memebrs status affected the iRule when they went down?

I'd appreciate any explanation.

Regards,

Sarah.