Is this down to a specific HST failure?
Something I've been harking on about for months, how to objectively measure the change.
How can the overall performance, intro and success/failure of the HSTs be accurately and objectively measured and fairly compared to what came before?
Those who are prejudiced against the HSTs will leap on any individual failure and laud the "good old days" of the 170s, when, in fact, plenty 170s failed too and plenty are glad to see the back of them for other reasons - primarily, lack of comfort and capacity. Whereas pro-HST people, like me, would say the first couple of days of such a huge change have, on the whole, been a success.