I have not heard of it happening in the restorative or perio patient parts of NERBs. Likely if a 'critical error' is made during one of the above (ie: an automatic failure) you will be told by one of the floor examiners. Examples: Visibly open contact on your new restoration. Failure. Examiners will ask you to remove the restoration (amalgam/composite) and place a temporary (IRM).
You will not know if you failed the prosth or endo until you get your scores.