In interest of full disclosure…this is not my idea. It is, however, a good idea.
Have your client call your cellphone on their cell phone. That connection will be on for the duration of the video session
When their call comes in, MUTE your phone. This will prevent feedback from the two microphones.
That way, you have a second communications channel already open if the session locks up.
You can instruct them to re-Join the session, suggest an alternative method or time, or continue by phone.