I have a client that has an Electra Elite IPK using Dterm80 phones with 3 lines and 6 extensions (101-106). With all phones plugged in except for 103, all 3 lines ring on all phones (as they should). When 103 is plugged in, line 3 only rings on 103 and everyone else is unable to pick up the call on their phones. Need Help!

What do you have on 4-01 and 4-02?

also, did you run the Dterm Diagnostic on the Dterm at x. 103? unplug the phone, hold * and #, plug in the phone. Release * and #.
Follow the instructions on the display to verify the function of all buttons, lights, and tones on the Dterm. When finished, lift the handset and hang up.

Sounds like line 3 has been set as DIL to extension 103