For instance, the crew that signed out an F700 I presented them with for a Lightning accepted it as serviceable (and airworthy). When a pressure regulator failed, and the relief valve jammed, the radome blew off and 2 Avons got a nasty attack of indigestion. Fortunately in that case Martin-Baker provided an alternative let-down procedure. And there were enough bits left to ascertain the cause.
In this case probably the actual cause will never be known.
Pilot error is one (of many) possibilities. It is unfortunately the one seized on by a pair of senior officers to obscure serious failings in their empires, and one which the crew are unable to offer any defence.