iRule node directive not working with SSL terminated virtual server

I'm having trouble with an iRule running on a virtual server handling https traffic - specifically with the "node" directive. The situation:

I have a pair of virtual servers, I'll call them Port80 and Port443, serving a web farm. Obviously Port80 receives http traffic and Port443 handles https traffic, configured with SSL termination so its pool is port 80 based (which the Port80 VS also uses). The 2 VSs share the same cookie based persistence profile. This iRule works on the Port80 VS and doesn't on the Port443 VS:

when HTTP_REQUEST {
  if {[string tolower [HTTP::uri]] contains "_monitor" } {
     switch -glob [string tolower [HTTP::uri]] {
        "*prodapp2*" {
           node 192.168.196.23 }
        "*prodapp3*" {
           node 192.168.196.33 }
        "*prodapp4*" {
           node 192.168.196.43 }
     }
  }
}

Obviously this is to allow external "server alive" monitoring of the individual nodes within the web farm. I'm currently doing this in my test environment and this is the only iRule in play. Consider a browser which currently has a persistence cookie for the prodapp3 node:

http://myDomain.com/_monitor/serverTest.aspx - works, response from prodapp3
http://myDomain.com/_monitor/serverTest.aspx?s=prodapp4 - works, response from prodapp4

https://myDomain.com/_monitor/serverTest.aspx - works, response from prodapp3
https://myDomain.com/_monitor/serverTest.aspx?s=prodapp4 - does not work, browser time out, it is as if the F5 dropped the request

The same thing happens if I don't use the serverTest page:

http://myDomain.com/anyPath/anyPage?_monitor=prodapp4 - works, response from prodapp4
https://myDomain.com/anyPath/anyPage?_monitor=prodapp4 - browser time out

I have tried other methods of specifying the node, changing "node 192.168.196.43" to:

node 192.168.196.43 80 - I get a response but from the persisted server, not the server specified in the query string
pool myPool member 192.168.196.43 80 - same (response but from wrong server)

Does anyone have an idea what I'm doing wrong and/or should do to make it work.