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