Conference ends when the person leaves from conf. who starts the conf. first.
Is it by design?
Here is my config
I apply this template to all phones.
softkeys hold Newcall Resume
softkeys idle Newcall Redial Pickup Gpickup Cfwdall Dnd
softkeys seized Endcall Redial Pickup Gpickup
softkeys connected Endcall Hold Trnsfer Confrn ConfList
Have you checked out this command;
conference drop-mode [creator | local]
Router(config-ephone-template)# conference drop-mode creator
(Optional) Configures the mode for dropping parties from multi-party ad hoc conferences.
â¢creator-The active conference terminates when the creator hangs up.
â¢local-The active conference terminates when the last local party in the conference hangs up or drops out of the conference.
From this good doc;
Hope this helps!