My guess. Supposed to be an easy fix. Crew sked has the crew come to the airport for a late morning departure. Repair goes awry for one of many reasons, and now the crew has started their duty day. Never go to the airport until the logbook is cleared, or you have a very strong guarantee from the ame who is actually working on the airplane.
Biggest fail here is probably the lack of real communications. Ultimately, there is now way that passengers should be sitting in Manchester for 48hrs with all the lift available in the UK this summer.
so why tell them to wait around for an 8 pm departure if their won't be a crew?
Seen it lots of times where they will try and guilt the crew into extending their duty day, even though it may not be legal