So reading through your process it looks like everything you are doing is correct to remove haze, however you did mention that when filtering one of your beers that it came out cloudier.
Now...I know nothing about filtering, but I do know that fining and temperature play a large role in the removal of chill haze. So as an experiment maybe you could fine & chill a future beer then split it, filter one batch and leave the other batch in the fridge at near 32f and see what happens after a couple of days?
Nothing in your process appears to point to the BM being the cause though.
Unless I'm not mashing long enough and my starch isn't converting all the way...