Garmin 595lm drops connection

Hello All I have a Garmin 595lm which works fine on my own as soon as a mate joins me on a ride and a intercom connection is made whilst navigating a route this knocks out the connection between my head set and my Zumo?
We are both useing Interphone Tours and have used Interphone 5mc with the same results I have replaced my zumo twice with battery faults and each unit did the same.
I do ware a insulin pump but keep it on aircraft mode when riding so my question is has anybody else experienced this problem?

 

Thanks for your reply I have contacted Interphone who have replaced my headset but that has made no difference I’ve also contacted Garmin who have replaced my 595 which also has made no difference.
Garmin did say they only test there units with one head set not connected via the intercom to another.