There are many reasons why a viva might be delayed.
Examiner or candidate illness could lead to a date change. Traffic or transport disruption could lead to a last minute change. Simple, random life stuff could force back the start time by half an hour on the day of a viva.
Whatever the circumstances, no delay to the viva – of weeks, days or minutes – will feel good.
To build up and get ready for meeting examiners and then have to wait could make someone feel extra-nervous; it might have other practical considerations too, like arranging childcare, checking transport options or having to rebook a room.
If it were to happen to you, remember that the feelings will pass. The situation will resolve. It won’t directly impact the viva itself. All of your preparation still counts. You might have a little longer to wait but you will still make it through.