It seems we might be in the same boat. I have a 185 pulley and noticed my belt "moving" a couple weeks ago and thought I was losing my mind. Then I looked carefully at all of the pulleys as the car was running(and I had removed the cooling fan for a better view). I noted that the serpentine belt was moving back and forth about 1mm each direction and also found that the belt was 1 rib off.........and hanging off of the back of the crank pulley. Then I came to the conclusion that the crank pulley was sticking out too far(farther than all other pulleys) and assumed it had somehow came loose. I then took my 650ft lbs torque 1/2'' impact and couldn't budge the bolt any tighter. I haven't told anybody about this issue yet as I figured it somehow had something to do with LET sending me the wrong replacement waterpump pulley(got one for an E55 V8 s/c) and didn't want to start throwing accusations. Here's some pics and a little video I made of my findings..........hopefully it's clear enough.



DSC06245.jpg

Note how the belt sticks out and hangs over the edge of the tensioner pulley............
DSC06246.jpg
DSC06248.jpg