Lync Dropping Calls After Call Waiting Passes Second Call to VM

Hey, everyone!

We're having a problem when someone is on a call and a second call comes in from there. Here is what is occurring:

1. You’re on a call with someone
2. Lync then prompts you that another call is coming in. 
3. You ignore it (just let it ring and not click the ignore button)
4. When that call then is pushed to voicemail (after 20 seconds), the call you’re currently on is disconnected.

We've also tested answering the second call. This results in the first person being put on hold and then silence on both ends of the second call.

This is also happening no matter if the call is a Lync call or an external call.

I did some Googling, and found a lot of references to changing these settings:

Set-CsTrunkConfiguration -RTCPActiveCalls $false -RTCPCallsOnHold $false

Is that what I should try to fix this problem as well?

I'm not seeing any errors on the server-side of things, but since it's happening on Lync-to-Lync calls as well as across multiple clients, it has to be something on the server side. Updating this mediation server setting seems to make sense to me.

I'd value anyone's input before making this change, though.

Thanks!

-Eric