Silence when adding a third party to Teams call

[HareBear]

We have an issue with a user (a Director) where if he adds someone to a running teams call e.g. connected to another employee and adds in HR person, then all sound is lost for 4 minutes or more.
If the  user creates a meeting then all is ok, even adding a new person mid meeting.

We have run Teams updates, updated to the latest audio and video drivers and tried a the same senario with different users on the same devices and it works ok.

Has anyone got an ideas please, its a real head scratcher.

Thanks

[#2]

I and some of my colleagues have had the same issue. Everytime I'm on a 1-on-1 call and a third person gets added. I'm guessing it has to do with the fact that I have Teams installed on my phone as well, as it sometimes says that I'm already on a call on a different device when I leave the call and try to rejoin.