FreePBX + VVX400 phone

Hi, tried to find answer for my question before asking.

I have a freepbx system, multiple VVX phone from polycom.

Im having issues, one of the 2 dispatch, both on the same ring group, when he pickup the line when ringing, phone take a second line insted of answering the ringing line. i changed phone for a new one, tryed multiple firmware, reset and etc.

Anyone has a clue for me?

thanks