Generally you cannot Fail a PAT Test, it is individual items that can Pass or Fail whether its the item itself the cable or the plug top. There are many reasons for this including - damage, wear and tear, deterioration, being counterfeit, incorrect termination and not meeting British Standards.
Carrying out a thorough visual inspection is very important and picks up the majority of Fails and the PAT Testing Equipment continues to look for deterioration and incorrect values.
All items that Fail are labelled, documented, removed from service and reported to the relevant Duty Holder, supervisors, customers and contractors for their disposal.
Sometimes the Failed appliance just need repairs and once completed often Pass, others are beyond repair and left for disposal. Unfortunately counterfeit items are rife and all too often sold to unsuspecting individuals, found through a visual inspection these need to be removed from use and disposed of.
Below are a few useful links for, HSE - Defective items in the workplace, Electrical Safety First - Spotting fake items and Gov.uk - Products recalls and alerts for unsafe products and resources for consumers, businesses and regulators.