What happened to the S Stock deliveries?

Hi. I was surfing on wikipedia and I saw an article about the S Stock. The article is below.
Why are all the S Stock deliveries subject to hiatus?


http://en.wikipedia.org/wiki/London_Underground_S_Stock#Entry_to_service

Cos they are subject to ongoing reliability problems. Bombardier - need I say any more?

Well, the most reliable fleet in the UK (Class 357) was built by Bombardier. Their new 379s on NXEA are also proving very reliable in their first year.

LOL. When they were B.R.E.L. Derby they somehow got to be in charge and send out stupid orders to us, at Wolverton, when at the time all trains had the Wolverton Lighting System; them telling us how to do it. Then they made a rather famous prototype with water powered brakes and forgot to add anti-freeze. They may be impressed with their own track record but the rest of what was B.R.E.L. know the truth.

Oh yes, and to prove how far off the ground their heads were, shall I mention the British Rail Flying Saucer patent?

Charles Osmond Frederick is a British engineer who worked on interaction of rails and wheels at the British Railway Technical Centre, Derby.

In 2006, patent-spotters rediscovered a patent attributed in 1973 to the British Railways Board on a nuclear driven space vehicle, dubbed the British Rail flying saucer. The patent was based on work performed by Frederick, which originally was directed towards a lifting platform and finally culminated in a nuclear fusion powered passenger craft for interplanetary travel.

A group of nuclear scientists examined the designs and declared them to be unworkable, expensive and very inefficient, so nothing much has changed in Derby since privatisation.