Three user.conf entries to the same SIP proxy - issues

I have three Gizmo Project/SIPPhone numbers/accounts, for three different people, that I am attempting to manage on my Asterisk v1.4 (w/Asterisk GUI). I have configured them via the GUI, then added ‘insecure = very’ to the users.conf after they have been generated.

With this, I am getting some erratic behavior. Where calls coming in from the SIPPhone proxy appear to be picking up the last entry in users.conf rather than the correct one. Is this something to do with users.conf (new to me) or with Gizmo. Ideas?