If you're still having problems, I'd check back again with Apple.
My old MB was having issues with screen flickering. This was several years ago so I don't remember all the specifics, but I narrowed it down to 2 parts, both of which required me to take a lot of the MB apart. The parts were going to cost around $100, and I didn't even know for sure if that was it.
Apple was able to give me a quote over the phone (got lucky??) and said they could do it, parts and labor, for $50. When i got there, the guy noticed a small chip on the top cover (this was an issue with this MB model) and said they HAVE to replace it, and since they're opening everything up the labor would be free. When I went to pick it up, another guy saw I was only paying $10 for the part, said he didn't want to deal with that, and handed me my very nice looking and fixed MacBook.
Magical.