As for those failings, let's start with those which have nothing to do with the location. Whilst not irritatingly 'stagey' like that of Closer, too often the dialogue here is clumsily unrealistic, with characters delivering lines too obviously scripted to convey information to the audience rather than the designated interlocutor on screen.
There's no attempt at disguise and Allen has made things harder for himself by crafting his story with such one dimensional characters out of whose mouths any sort of nuance would have seemed unrealistic in its own way. Having given this aspect of the film some consideration, I'm not so sure however that it is a failing as such. Jonathan Rys-Myers delivers and eerily empty performance as retired tennis-pro Chris Evans, inscrutable in his calculating moral detachment. If any of the other main players had been more rounded, the subtlety of this impersonation might have been drowned out. (The script does her few favours, but Johansson appears to be trying hard with Nola, especially drunk Nola.)
Anyway, the real problems here have to do with the switch from NYC to London, facilitated by a load of dosh from the BBC. Maybe there wasn't time to rethink the narrative too carefully, but the first sign of trouble shows up with Evans apparently using a knowledge of Dostoevsky and opera and presenting himself generally as "non trivial" in order to gain entry to the upper echelons of British society. Like that would work!
Back in Manhattan of course, there's a much clearer association between high society and high culture, between cosmopolitanism and support for the arts (as well as charity in general).
Only recently I was at one of London's leading arts venues with Frode. and having noted how unaffected our fellow audience-members were, he duly confided to me that the realisation had come to him rather belatedly in life that New York is a far more snobbish, class-based environment than London. This didn't come as news to me, as I recalled my father's experiences when he opened an office over there in the 80s and his future partners attempted to impress him with evenings at the sick-making University Club. And then there was my own visit to the Met last May, where the lobby's fill up with individuals one would hesitate to describe as unaffected.
Our class system is not non-existent for sure, but for outsiders it's certainly a bit of a minefield and Allen comes out of this little foray into it minus his foot. Brian Cox has been about as miscast as his namesake the TV professor of physics would have been as the country pad patrician. And the lines this bizarre family deliver are packed with jarring solecisms, bogus 'U' vocabulary and bizarre non-sequiturs; my personal favourite being "I grew up in Belgravia, so...", largely because I could say it myself, but of course wouldn't.
I suppose this may be an issue which is only going to bother us Brits. But there are subsidiary issues of verisimilitude. I mean, how likely is it that two tennis players from these islands good enough to play on the main ATP tour, would meet by chance on Old Bond Street? A location Allen reuses for yet another non-tennis related fortuitous encounter in the movie. This was surely intended to be Fifth Avenue in the original conception. I wonder whether it also had Nola penciled in as a Brit?!