[gruntygiggles]

I don't believe there are fail quotas. Training centres rely on their pass rates to continue to attract customers...they would not stand by and allow there to be a fail quota. To have a fail quota would be to open themselves up to constant scrutiny.

If you fail, you have ridden in a manner for all or part of the test that your examiner is not happy with. I don't doubt that every now and then an examiner takes a dislike and judges harshly for no good reason, but you have to, iirc, bring it up then and there.
I am still wondering how that junction worked to be turning right at a t junction but be 10 inches from the right kerb?