Issues renaming fields

I am having issues with renaming a large number of fields, I am trying to create them as nested fields to organise them better in elastic. I keep getting _mutate_error and also this in the log.

{:exception=>"class org.jruby.RubyString cannot be cast to class org.logstash.ConvertedList (org.jruby.RubyString and org.logstash.ConvertedList are in unnamed module of loader 'app')"}

Is this "scheme" below suitable? Is there some kind of order that I should be doing these renames in? or breaking them up into separate mutate blocks?
Wondering if its even worth it and I just stick to the original field names?

mutate {
        rename => {
            "application"                       =>  "[application][name]"
            "applicationid"                     =>  "[application][id]"
            "skillset"                          =>  "[skillset][name]"
            "contacttype"                       =>  "[skillset][contact_type]"
            "skillsetid"                        =>  "[skillset][id]"
            "site"                              =>  "[skillset][site_name]"
            "siteid"                            =>  "[skillset][site_id]"
            "skillsetabandoneddelay"            =>  "[skillset][stat][calls_abandoned_delay]"
            "callsanswered"                     =>  "[skillset][stat][calls_answered]"
            "callsansweredafterthreshold"       =>  "[skillset][stat][calls_answered_after_threshold]"
            "callsanswereddelay"                =>  "[skillset][stat][calls_answered_delay]"
            "callsoffered"                      =>  "[skillset][stat][calls_offered]"
            "skillsetabandoned"                 =>  "[skillset][stat][calls_abandoned]"
            "skillsetabandonedaftthreshold"     =>  "[skillset][stat][calls_abandoned_after_threshold]"
            "maxanswereddelay"                  =>  "[skillset][stat][max_answered_delay]"
            "maxskillsetabandoneddelay"         =>  "[skillset][stat][max_skillset_abandoned_delay]"
            "netcallsanswered"                  =>  "[skillset][stat][net_calls_answered]"
            "virtualcallsoffered"               =>  "[skillset][stat][virtual_calls_offered]"
            "virtualcallsabandoned"             =>  "[skillset][stat][virtual_calls_abandoned]"
            "virtualcallsabnaftthreshold"       =>  "[skillset][stat][virtual_calls_abandoned_after_threshold]"
            "dnoutextcallstalktime"             =>  "[dn][outbound][external][talk_time]"
            "dnoutintcallstalktime"             =>  "[dn][outbound][internal][talk_time]"
            "activetime"                        =>  "[skillset][duration][active_time]"
            "allagentbusytime"                  =>  "[skillset][duration][all_agents_busy_time]"
            "talktime"                          =>  "[skillset][duration][talk_time]"
            "waittime"                          =>  "[skillset][duration][wait_time]"
            "maxcapacitytotalstaffedtime"       =>  "[skillset][duration][max_capacity_total_staffed_time]"
            "maxcapacityidletime"               =>  "[skillset][duration][max_capacity_idle_time]"
            "idletime"                          =>  "[skillset][duration][idle_time]"
            "notreadytime"                      =>  "[skillset][duration][not_ready_time]"
            "totalstaffedtime"                  =>  "[skillset][duration][total_staffed_time]"
            "postcallprocessingtime"            =>  "[skillset][duration][post_call_proc_time]"
        }
    }