iRule RAM CACHE odd behaviour

Quick thought... you're using HTTP::uri, not HTTP::path. The URI could have other data (query strings, etc...) at the end, which could be messing with the ends_with setting. We usually do something more like (where 'static_content' is a data group of extensions we want cached):

set VsRAMCacheState [PROFILE::http ramcache]
set content_extension [string range [HTTP::path] [string last . [HTTP::path]] end]
if {  $VsRAMCacheState == 1 } {
    CACHE::disable
    if { [ class match $content_extension equals static_content ] }{
        enable
    } 
}