UPDATE 23rd June 16:45
The problem is resolved. We will be contacting affected organisations shortly.
23rd June 10:55
Under rare circumstances, emailed guest invitations sent from within ongoing calls can contain errors in the subject line. Vitalhub is aware of the problem and is working on a solution. We will update when we have more information. Until then, in-call invitations should be made by SMS or using the second method in this guide, described on page 2.