It took quite some months, three failed repairs at the Apple Premium Reseller, a lot of calls and most of all a lot of patience and waiting, but I finally received my new (actually new, as in: sealed) 15" MacBook Pro.
I know new issues can possibly pop up again after (little) while, but for now I am just tremendously happy. I feel like a little kid, man. So far no issues concerning strange popping/clicking/creaking issues which I had before (nor do I have any keyboard issues - which I had before).
Please note that Apple eventually offered me a 15" MacBook Pro 2017 version, while I initially purchased a 2016 version. That is because I had gotten three repairs already, and Apple decided to take care of things themselves after I called them. If it was just my first repair or so, I should have just gotten a display replacement and it should have been solved - so I have been told.
So in fact I went through quite some trouble and was stuck with a faulty laptop for quite some time as well, but I basically ended up with a newer and slightly "better" device for the same price. Well that is positive! I hope I do not have that much bad luck this time when it comes to the defects, however. And getting the old laptop picked up and swapped with a new one was pretty much horror as well, but oh well. Apple tried to solve matters the best they could, even though it was a problem regarding an external delivery company or something. But their communication was great, and their customer service was extremely friendly and personal and just ... nice? I never expected this from Apple, to be honest, so I am pleasantly surprised. I am even getting a call in a week or so because they want to check if everything is working properly and went well.
I hope you guys get a proper fix as well. Maybe some people call some defects like this nitpicking, but you paid this much for a device so it should function properly as well.