Our uc540 has recently developed a fault where other phones in the group keep ringing after a call (via sip) is answered. This wasn't a huge problem as if someone answered one of the still ringing phones, they just got a dial tone, however, after a recent power cut it has now got worse, it keeps ringing for 20 or so seconds after the call is answered and if someone answers one of the ringing phones it steals the call from the person who is, by now, in mid conversation!!
Does anyone have any pointers as to how I can troubleshoot this issue? Unfortunately I only really know how to use CCA so cli commands won't really be much help to me.