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.
ephone-template 2
conference admin
network-locale 1
user-locale 1
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
keep-conference endcall