Interesting, --id--.
I thought this was likely to happen to me if I sent it in enough. Have you settled with the issue now? Or will you send it back since the problem persists?
I am planning to send it in again, but since it is my main working machine I have to wait a few weeks because I need it now. I bought it from a premium reseller in Austria (McSHARK) and and also brought it there for the repair. They repaired it in-house the first time and ordered the replacement top case from Apple. The whole process was quite quick (5 working days from drop-off to pick-up) and they also acknowledged the problem right away and said that it was a known problem. When I picked up the machine after the repair I tested it on their counter (with multiple "yes" commands in terminal) and it seemed that everything was fine, but in the course of the following days the popping started again...
I hope, like you, that eventually they will give me a replacement after a few unsuccessful repairs. I am looking forward to hear your experience after you get your machine back!