I looked at a car I was considering for purchase from a third party and brought the car to BMW of North Haven for their, not inexpensive, "Certified Pre-Owned" bells and whistles pre-purchase inspection. While they seemed to be very competent and helpful, picking up on many small items (vapor barriers on doors in need of replacement, missing battery vent tube) they missed the fact that the car had a major issue: a cracked valve cover. The dealer from whom I purchased the car, after the all clear from North Haven and discovery of the issue, was rather surprised North Haven had missed the cracked valve cover; so was I !
I then discussed the problem with North Haven and they simply said they stood by their inspection and that discovery of the cracked valve cover, even though the car was mis-firing, was not an oversight on their part. They even suggested the cover had cracked in the short time between the car leaving their shop and my driving it home. They refused to make any accommodation on the price of their expensive inspection. Thankfully, the excellent dealer from whom I bought the car (J&M Automotive) did the right thing and covered a significant part of the repair cost with my own mechanic, though they had no obligation to do so. An excellent example of fantastic customer service, side-by-side with an example of very poor customer service.