What happens if you fail your PhD viva?

Have you considered that you are fixated with this person?

There are more outcomes than "pass/fail" for a PhD defence as I understand. They can also be given a pass with minor/major corrections - if so then they will be revising the thesis with the corrections noted.

Most people pass subject to corrections, you are dealing with a thesis covering 4 years research which is 50-100,000 words, typically 200-400 pages and it is examined by a world expert in your field.

It is near impossible to have a perfect thesis (however hard you try) and the examiner will no doubt have their own opinions. A very small percentile of thesis pass with zero corrections (and this is probably a reflection of the examination more then the thesis).

Corrections are mostly minor such as re-formatting data, typographic, small amendments (generally less then 3 months although you may be given up to 6 months, especially if you are working full time elsewhere p), however they can be major (most people really want to avoid this) where more substantial changes are needed and you may need a second viva.

If they are still working very hard it is probably because:
- they just want to get the amendments asap made so they can move on
- they have something else brewing such a new job, research position... and they want the corrections sorted so they don’t have to balance fitting it in whilst they hold another job
- maybe they are writing papers or submitting new funding applications or research proposals...
- perhaps they are just passionate about there research & are eager to look into things there examiners brought to there attention

There really is a host of stuff.

It doubt it'd minor amendments as the person is working a few days after their viva and its coming so early and till Saturday so seems like a 2nd viva situation or something

Perhaps, but what if they have a months worth work and they just want to smash it out... impossible to say.