Hello!
Asterisk Asterisk 14.2.1
Linux srv-astrisk 3.10.0-514.6.1.el7.x86_64 #1 SMP Wed Jan 18 13:06:36 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
I have had a very strange situation and I have no idia what to do 
At 11:00 user “A” have made a conference for some users… And this conference took a long time…
At 11:29 user “B” have called to user “C” and the conversation began.
At the same time, all users in conference of user “A”, started to hear the conversation between users “B” and “C”. But not permanent, voices appear with wheezing and interference, then disappear and than appear again.
According to those, there was a feeling that someone turned on and off the microphone for a speakerphone … One of the conference participants recognized the voices of user “B” and “C” and tried to convey that they were heard in the conference, but no response followed by …
But, in the call between the user “B” and "user “C” they didn’t hear extraneous sounds and the voices of users in conference.
After the speaker who recognized the voice dialed one of them on the mobile and said that they were audible, the conversation between “B” and “C” was completed, putting the tubes …
The conference continued on in normal mode …
Based on the words of all users, logs and cdr:
- All calls have different call IDs …
- No strange processes were detected at this time …
- The conversation began to be heard not from the very beginning, but audibility appeared, then disappeared in a floating mode somy times…
I hope that at least something is clear from the description 
Can someone come across a similar.
Or sombody knows where to dig, what to watch?