I believe that the only "perfect" masters are those that may exist in the the pages of old Zen stories, written when the real folks were long dead, scrubbing them clean of every blemish and failing. In fact, if we might travel back in time to meet these fellows "in the flesh," we would find that each and every one was probably just "people" like you and me, with good points and (likely) a few rough edges and minor bad habits... like all people. Okay, maybe extra-ordinarily Wise and Compassionate and Enlightened, sure ... but people.
Of course, "Enlightenment" is a realization that there is no place to fall, no self to stumble, no "mistake" that can ever be made. That is true. But it is just as true that there is no place to fall, no stumbling or possible mistake... even as we may fall and stumble and make mistakes!
A few days ago, an excellent article by Lewis Richmond appeared here on SunSpace entitled "'What If?' Guidelines for Choosing a Buddhist teacher". I would really like to recommend that article to everyone. If I may add my own "test" for finding a teaching, I would say find a man or woman who sometimes falls down, makes mistakes, makes a donkey's ass of him or herself... and observe closely what happens, watch how he or she does it. Oh, don't get me wrong... probably you do not want as a teacher someone who falls down each and every day, nor someone who falls down too BIG (robbing banks, lying profusely and intentionally starting fires, for example). No, I mean someone who... every so often, now and then, like everyone... makes a fool of him/herself, loses his Zen Master cool, over-indulges, does a real face-flop, says something she regrets, breaks some (hopefully not too big) Precepts in some very human way.
How does this person recover their balance? With what grace do they fall or, at least, get back up on their feet? Do they profoundly reflect on their mistakes, learn from them, apologize sincerely to anyone hurt (hopefully not too badly) ... and move on? As a matter of fact, since this crazy practice is greatly about living with some grace in this imperfect, often disappointing, trap and temptation filled world, a teacher with a couple of serious imperfections may be a good guide on how to avoid, lessen or escape the worst of it!
All human beings have the tendency to fall down from time to time. I guess it is just a matter of what the person does then ... picking themselves up, recovering balance, getting back on the trail, apologizing and learning from any damage caused. Like any great athlete, the point is not that we never get knocked around, never trip or stumble ... but how we handle the fall (as in the martial arts ... there is no training offered on how to never fall, but endless training on how to fall well). Show me the man or woman who falls down sometimes ... but who demonstrates how to fall well and recover one's footing ... and I will show you a great Zen teacher.