URL partially able to open in the Chrome & IE, but able to open in Firefox

Actually I have a feeling that your requests are landing to a member which cannot serve it. I see you have 2 different ports and your logic is requesting to fulfill from one particular pool member alone.

If your default pool is consisting both the above mentioned pool members and if you know for sure that one member cannot server certain requests, you have to identify them. And write some logic to it. So that it lands on the right pool member & it can server it properly without dropping.

One way to easily find is by putting a logging to see which pool member had it served for every requests.

Add a new IRule and map it to the virtual & see the results. Or modify in the existing one itself.

when CLIENT_ACCEPTED {
set client [IP::client_addr]
log local0. "Client: $client has established a connection"      
}
 
when HTTP_REQUEST {
set client_info [IP::client_addr]:[TCP::client_port]
set url [HTTP::header Host][HTTP::uri]
log local0. "Client Source IP: $client_info is requesting URL: $url " 
}
 
when SERVER_CONNECTED {
set pool_name [LB::server pool]
log local0. "Client Source IP: [IP::client_addr]:[TCP::client_port] <--> POOL : $pool_name <--> ACTUALNODE <--> [IP::server_addr]:[TCP::server_port]" 
}

Hope it helps.