On my 2001 528i, the camshaft position sensor failed. I had it replaced at the dealer and now have a small oil leak coming from the front of the motor somewhere (not determined thus far). Is it possible they didn't install the o-ring properly? I called them back and made an appointment and was told they'd "cover the costs if it were a result of the camshaft sensor replacement" but otherwise it would be at my expense. It's never leaked a drop until now, and I would like some feedback to support my theory if necessary. Thanks!