"several operational circumstances" does not strike me as any proof of an "extraordinary circumstance." Presuming that your information regarding technical faults is correct, then you should be entitled to compensation.

BA having denied your claim, you have several options:
1. If you have a UK address available to you, file an MCOL action. You will need to send a Letter Before Action. Forms available on the MCOL website.
2. File a CEDR claim. In order to do that, you need a final response letter from BA.
3. You may also file a small claims action against BA. Telephonic hearings are available and this may be the easiest route if you do not live in the UK.

All of the above may cause BA to reevaluate or provide better information as to why it is correct. Keep us posted.