[susan53]

The number of problems doesn't necessarily reflect the final "quality" of the pronunciation. It also depends how much those problems affect intelligibility. If for example a German speaker pronounces "very good" as "wery goot" it may still be intelligible despite there being a mispronunciation in each word. In another case one mispronounced sound might make the whole thing unintelligible.

Of the learners I've taught, it's tended to be Spanish spekers who have the greatest problems arriving at a level of accuracy which is intelligible. Interestingly, one of their problems is also final consonant clusters - in this case with /t/ or /d/, as in "test" or "laughed".