How to determine last segment in reaseembled TCP packet

As a test, you could try making each log message unique with a global counter. I wouldn't suggest using this in production as it's unnecessary overhead.

 
 when SERVER_CONNECTED { 
    TCP::collect 
 } 
  
 when SERVER_DATA { 
  
    if {[info exists ::counter]}{ 
       incr ::counter 
    } else { 
       set ::counter 1 
    } 
    log -noname local0. "iRule: Received Server Data $::counter" 
    TCP::collect 
    TCP::release 
 } 
 

You might also try removing the -noname flag and see if that has any effect.

Aaron