I have a few questions for you as I have one of these in transit. First, have you contacted Todd at FFT and shared these concerns with him. Having spoken with him on a few occasions, I know he would be interested to find out that one of these units might be problematic.
Second, do you have any photos you could share that show the problems you are having? I know that Benelli restricts forum privileges until you have a certain number of posts but there are ways around that. Pictures would go a long way in terms of helping to understand the issues you are having.
Third, how old is your M4 and what kind of condition is it in? I ask because if it's older or has been banged around a bit, there is a good possibility that the tolerances may be indeed off a bit and may account for the issues you describe.
As I said earlier, your best bet would be to contact Todd at FFT and describe what is happening. I would think that you might get better satisfaction from doing that as opposed to writing what I consider to be an incomplete review on an internet forum.
"Pain or damage don't end the world. Or despair, or ____ing beatings. The world ends when you're dead. Until then, you got more punishment in store. Stand it like a man.........and give some back."