I heard a story once about an American guy whose grandparents had emigrated from italy going there on his holidays with 'fluent italian'. He couldn't make himself understood at all and finally realized he was essentially speaking nineteenth century neapolitain.

To those struggling. If you listen to quite a few diiferent recordings it might help. (Or you might end up horribly confused by versions from donegal when your original was from cork or something, but there's always a bit of risk in life.)