I use freepbx distro, it’s work fine for over a year, last month call local extension get mess call extension A then it ring on extension B. I’m delete both extension then re-create then it’s ring to right extension.
Now it’s happen again with other 2 extensions
Local dial extension A but ring on phone with extension B.
Check to see if extension A has been call forwarded to extension B.
You can call forward from some phones via the soft keys, however you can also call forward by hitting the keystrokes accidentally. You can print extensions to display the call forward keys.
Also, check extension settings for those extensions also in the gui.