Are you finding that you are getting better at asking the kinds of questions whose answers identify potential problems that would have otherwise only been apparent after you had accepted the job? It's just possible that this might be too much to ask, especially if the problems are sufficiently different every time. The answer to the 'is it me' question may quite possibly have less to do with your compatibility or suitability but may have more to do with 'diagnostic skill', in which case, perseverance may just pay off as you get better at it over time.