None of those reasons look like extraordinary circumstances which would relieve the airline from their obligations for compensation.
The CAA page on the topic tells us:
The UK law on flight compensation uses the term 'extraordinary circumstances' to refer to situations where delays or cancellations have been caused by things that are not the responsibility of the airline. If extraordinary circumstances apply, you are not entitled to compensation.
The Regulation does not define “extraordinary circumstances” and there have been a number of cases in the European (before the UK left the EU) and English courts regarding what the term covers. The cases have centred on whether technical faults on an aircraft could be an extraordinary circumstance. In June 2014 the English Court of Appeal issued a judgment in the Jet2 v Huzar case which provided clarity in the UK that technical problems were not an extraordinary circumstance.
In September 2015 the European Court looked at the same issue in the case of KLM v van der Lans. The court found that technical problems were not extraordinary and neither was the early failure of an aircraft component. The ruling noted two types of technical fault that may be extraordinary, a hidden manufacturing defect and damage to an aircraft caused by sabotage or terrorism.
Examples of extraordinary circumstances
The main categories of events that are likely to be an extraordinary circumstance include:
- Weather conditions incompatible with the safe operation of the flight
- Strikes (unrelated to the airline such as airport staff, ground handlers, air traffic control or border force)
- Acts of terrorism or sabotage
- Security risks
- Political or civil unrest
- Hidden manufacturing defects (a manufacturer recall that grounds a fleet of aircraft)
"Weather conditions incompatible with the safe operation of the flight" is like a storm or a blizzard, not "rain leaked into the aircraft causing a technical fault".
Are they actually alleging extraordinary circumstances, and what reason do they give for that?