Fully. It's really is a shame but I'm surprised by some of the posts in this thread. Personally I wouldn't trust Stones in a high pressure big game at all. His consistency over 90 minutes is piss poor. Bit like Otamendi, he's got a terrible habit of giving up one guilt edge chance to the opposition every 90 minutes. And that's before we get into his terrible physical condition.
For me, it's neither of those things, although both are a problem, it's that he doesn't play like John Stones anymore. His passing is safe and boring, he hesitates, he never really carries the ball out any more - he has completely lost his swagger. Remember when he shushed the Everton crowd after they shit themselves because he was playing in his own box? He'd never do that any more. He seems mentally destroyed by so many high profile errors.