Another "Service Engine Soon" question!

My 2011 335i, with less than 5500 miles on it, had the "service engine soon" light come on around two months ago. I made sure the gas cap was tight, but the light remained on, so a week later I took the car in to the dealer. The doggoned light went out before I got there, and they found no fault code, so they sent me on my way. The light reappeared a week later (the fuel cap hadn't been touched in the meantime) so I made another appointment. Again, the light went out the day before, but now something new....all my FM and satellite presents were gone, and the three buttons for directing vent air were all lighted. I never touch them, so I knew there was a gremlin.

This time they did get a code, and replaced a faulty fuel tank pressure valve. Two weeks later the light came on again, so I brought the car back once more. They got the same fault code again, so they had to order a new valve. It arrived yesterday and they installed it. Following this they had to re-install a software package, and the installation kept freezing at the same point, so they called BMW and were told to replace a certain module that was causing the freeze. I believe it controls some interior lights. Why do I have little faith that the problem has actually been solved?

Has anyone had this specific problem, and if so, what solved it? The car was supposed to be ready this afternoon, but they still have it. I kind of assume they'll call at closing time with more bad news!