Users of my phone system are reporting a couple issues:
1 - if they are already talking to someone on the phone, and a second call comes in (they are part of a ring group) the person they are talking to is able to hear the ring on the line interrupting the conversation.
2 - occasionally when the above happens, the interrupting ring will literally hang up whatever phone call they are on.
This is using FreePBX 2.9.0.7 on asterisk, with aastra 9143i handsets.