Depends on who's doing the pronouncing, I suppose, but certainly linguists are not competent in all languages. Two obvious examples occur to me. The first is

Depends on who's doing the pronouncing, I suppose, but certainly linguists are not competent in all languages. Two obvious examples occur to me. The first is the clicking sound in some African languages. Another is a speaker accustomed to a limited set of vowels trying to input vowel sounds he can't replicate well.